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• I thought everyone did it like this – Training Session Code Management

  - by Fatherjack

  One of an occasional series of blogs about things that I do that perhaps others don’t. From very early on in my dealings with SQL Server Management Studio I started using Solutions and Projects. This means that I started using them when writing sessions and it wasn’t until speaking with someone at PASS Summit 2013 that I found out that this was a process that was unheard of by some people. So, here we go, a run through how I create and manage code and other documents that I use in presentations. For people unsure what solutions and projects are; • Solution – a container for one or more projects. • Project – a container for files, .sql files are grouped as Queries, all other files are stored as Misc. How do I start? Open Management Studio as normal, and then click File | New and select Project This will bring up the New Project dialog box and you can select/add details as necessary in the places indicated. If this is the first project you are creating then be sure to select the Create directory for solution check box (4). If know in advance that you are going to have more than one project in the solution then you may want to edit the Solution name (3) as by default it will take the name of the project that you enter at (2). This will lead you to the following folder structure (depending on the location that you chose in 3) above. In SSMS you need to turn on the Solution Explorer, either via the View menu or pressing Ctrl + Alt + L                   This will bring up a dockable window that will let you quickly access the files that you choose to include in the Solution.                     Can we get to work and write some code yet please? Yes, we can. As with many Microsoft products there are several ways to go about this, let’s look at the easiest way when creating new code. When writing a presentation I usually start from the position we are currently in – a brand new solution and project with no code. Later on we will look at incorporating existing code files into the Project where we need it. Right-click on the Project name and choose Add New Query           As soon as you click this you will be prompted to select the sql server that you want to connect to and once you have done that you will have your new query open in the text editor and the Solution Explorer will now look like this, showing your server connection and your new query.               And the Project folder will look like this         Now once you have written your code don’t press save, choose Save As and give the code a better name than QueryX.sql. SSMS will interpret this as a request to rename Query1 and your Project and the Project folder will show that SQLQuery1.sql no longer exists but there is now a file named as you requested. If you happen to click save in error then right-click the query in the project and choose rename.               You can then alter the name as you like, even when open in the SSMS text editor, and the file will be renamed. When creating a set of scripts for a presentation I name files with a numeric prefix so that when they are sorted by name they are in the order that I need to use them during the session. I love this idea but I’ve got loads of existing scripts I want to put in Projects Excellent, adding existing files to a project is easy, let’s consider that you have query files in your My Documents folder and you want to bring them into the Project we have just created. Right-click on the Project and choose Add | Existing Item           Navigate to the location of your chosen file and select it. The file will open in SSMS text editor and the Project will be updated to show that the selected query is now part of your project. If you look in Windows Explorer you will see that the query file has been copied into the Project folder, the original file still remains in your My Documents (or wherever it existed). I’ll leave it as an exercise for the reader to explore creating further Projects within a solution but will happily answer questions if you get into difficulties. What other advantages do I get from this? Well, as all your code is neatly in one Solution folder and the folder contains only files that are pertinent to the session you are presenting then it makes it very easy to share this code, simply copy the whole folder onto a USB stick, Blog, FTP location, wherever you choose and it’s all there in one self-contained parcel. You don’t have to limit yourself to .sql query files, you can add any sort of document via the Add Existing Item method, just try it out. Right-click on the protect and choose Add | Existing Item           Change the file type filter.                       You can multi select items here using Ctrl as you click each item you want. When you are done, click the Add button and the items will be brought into your project.                 Again, using this process means the files are copied into the project folder, leaving you original files untouched in their original location. Once they are here you can double click them in the SSMS Solution Explorer to open them, for files with a specific file type then the appropriate application will be launched – ie Word, Excel etc. However, if the files are something that the SSMS Text editor can display then they will open in a tab in SSMS. Try it out with a text file or even a PS1 file … This sounds excellent but what do I need to watch out for? One big thing to consider when working like this is the version of SSMS that you are using. There is something fundamentally different between the different versions in the way that the project (.ssmssqlproj) and solution (.sqlsuo and .ssmssln) files are formatted. If you create a solution in an older version of SSMS and then open it in a newer version you will be given the option to upgrade it. Once you do this upgrade then the older version of SSMS will not be able to open the solution any more. Now this ranks as more of an annoyance than disaster as the files within the projects are not affected in any way, you would just have to delete the files mentioned and recreate the solution in the older version again. Summary So, here we have seen how using SSMS Projects and Solutions can help keep related code files (and other document types) together in a neat structure so that they can be quickly navigated during a presentation and it also makes it incredibly simple to distribute your code and share it with others. I hope this is of use to you and helps you bring more order into your sql files, whether you are a person that does technical presentations or not, having your code grouped and managed can make for a lot of advantages as your code library expands.  

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• Do you play Sudoku ?

  - by Gilles Haro

  Did you know that 11gR2 database could solve a Sudoku puzzle with a single query and, most of the time, and this in less than a second ? The following query shows you how ! Simply pass a flattened Sudoku grid to it a get the result instantaneously ! col "Solution" format a9 col "Problem" format a9 with Iteration( initialSudoku, Step, EmptyPosition ) as ( select initialSudoku, InitialSudoku, instr( InitialSudoku, '-' )        from ( select '--64----2--7-35--1--58-----27---3--4---------4--2---96-----27--7--58-6--3----18--' InitialSudoku from dual )    union all    select initialSudoku        , substr( Step, 1, EmptyPosition - 1 ) || OneDigit || substr( Step, EmptyPosition + 1 )         , instr( Step, '-', EmptyPosition + 1 )      from Iteration         , ( select to_char( rownum ) OneDigit from dual connect by rownum <= 9 ) OneDigit     where EmptyPosition > 0       and not exists          ( select null              from ( select rownum IsPossible from dual connect by rownum <= 9 )             where OneDigit = substr( Step, trunc( ( EmptyPosition - 1 ) / 9 ) * 9 + IsPossible, 1 )   -- One line must contain the 1-9 digits                or OneDigit = substr( Step, mod( EmptyPosition - 1, 9 ) - 8 + IsPossible * 9, 1 )      -- One row must contain the 1-9 digits                or OneDigit = substr( Step, mod( trunc( ( EmptyPosition - 1 ) / 3 ), 3 ) * 3           -- One square must contain the 1-9 digits                            + trunc( ( EmptyPosition - 1 ) / 27 ) * 27 + IsPossible                            + trunc( ( IsPossible - 1 ) / 3 ) * 6 , 1 )          ) ) select initialSudoku "Problem", Step "Solution"    from Iteration  where EmptyPosition = 0 ;   The Magic thing behind this is called Recursive Subquery Factoring. The Oracle documentation gives the following definition: If a subquery_factoring_clause refers to its own query_name in the subquery that defines it, then the subquery_factoring_clause is said to be recursive. A recursive subquery_factoring_clause must contain two query blocks: the first is the anchor member and the second is the recursive member. The anchor member must appear before the recursive member, and it cannot reference query_name. The anchor member can be composed of one or more query blocks combined by the set operators: UNION ALL, UNION, INTERSECT or MINUS. The recursive member must follow the anchor member and must reference query_name exactly once. You must combine the recursive member with the anchor member using the UNION ALL set operator. This new feature is a replacement of this old Hierarchical Query feature that exists in Oracle since the days of Aladdin (well, at least, release 2 of the database in 1977). Everyone remembers the old syntax : select empno, ename, job, mgr, level      from   emp      start with mgr is null      connect by prior empno = mgr; that could/should be rewritten (but not as often as it should) as withT_Emp (empno, name, level) as        ( select empno, ename, job, mgr, level             from   emp             start with mgr is null             connect by prior empno = mgr        ) select * from   T_Emp; which uses the "with" syntax, whose main advantage is to clarify the readability of the query. Although very efficient, this syntax had the disadvantage of being a Non-Ansi Sql Syntax. Ansi-Sql version of Hierarchical Query is called Recursive Subquery Factoring. As of 11gR2, Oracle got compliant with Ansi Sql and introduced Recursive Subquery Factoring. It is basically an extension of the "With" clause that enables recursion. Now, the new syntax for the query would be with T_Emp (empno, name, job, mgr, hierlevel) as       ( select E.empno, E.ename, E.job, E.mgr, 1 from emp E where E.mgr is null         union all         select E.empno, E.ename, E.job, E.mgr, T.hierlevel + 1from emp E                                                                                                            join T_Emp T on ( E.mgr = T.empno ) ) select * from   T_Emp; The anchor member is a replacement for the "start with" The recursive member is processed through iterations. It joins the Source table (EMP) with the result from the Recursive Query itself (T_Emp) Each iteration works with the results of all its preceding iterations.     Iteration 1 works on the results of the first query     Iteration 2 works on the results of Iteration 1 and first query     Iteration 3 works on the results of Iteration 1, Iteration 2 and first query. So, knowing that, the Sudoku query it self-explaining; The anchor member contains the "Problem" : The Initial Sudoku and the Position of the first "hole" in the grid. The recursive member tries to replace the considered hole with any of the 9 digit that would satisfy the 3 rules of sudoku Recursion progress through the grid until it is complete.   Another example :  Fibonaccy Numbers :  un = (un-1) + (un-2) with Fib (u1, u2, depth) as   (select 1, 1, 1 from dual    union all    select u1+u2, u1, depth+1 from Fib where depth<10) select u1 from Fib; Conclusion Oracle brings here a new feature (which, to be honest, already existed on other concurrent systems) and extends the power of the database to new boundaries. It’s now up to developers to try and test it and find more useful application than solving puzzles… But still, solving a Sudoku in less time it takes to say it remains impressive… Interesting links: You might be interested by the following links which cover different aspects of this feature Oracle Documentation Lucas Jellema 's Blog Fibonaci Numbers

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• Spooling in SQL execution plans

  - by Rob Farley

  Sewing has never been my thing. I barely even know the terminology, and when discussing this with American friends, I even found out that half the words that Americans use are different to the words that English and Australian people use. That said – let’s talk about spools! In particular, the Spool operators that you find in some SQL execution plans. This post is for T-SQL Tuesday, hosted this month by me! I’ve chosen to write about spools because they seem to get a bad rap (even in my song I used the line “There’s spooling from a CTE, they’ve got recursion needlessly”). I figured it was worth covering some of what spools are about, and hopefully explain why they are remarkably necessary, and generally very useful. If you have a look at the Books Online page about Plan Operators, at http://msdn.microsoft.com/en-us/library/ms191158.aspx, and do a search for the word ‘spool’, you’ll notice it says there are 46 matches. 46! Yeah, that’s what I thought too... Spooling is mentioned in several operators: Eager Spool, Lazy Spool, Index Spool (sometimes called a Nonclustered Index Spool), Row Count Spool, Spool, Table Spool, and Window Spool (oh, and Cache, which is a special kind of spool for a single row, but as it isn’t used in SQL 2012, I won’t describe it any further here). Spool, Table Spool, Index Spool, Window Spool and Row Count Spool are all physical operators, whereas Eager Spool and Lazy Spool are logical operators, describing the way that the other spools work. For example, you might see a Table Spool which is either Eager or Lazy. A Window Spool can actually act as both, as I’ll mention in a moment. In sewing, cotton is put onto a spool to make it more useful. You might buy it in bulk on a cone, but if you’re going to be using a sewing machine, then you quite probably want to have it on a spool or bobbin, which allows it to be used in a more effective way. This is the picture that I want you to think about in relation to your data. I’m sure you use spools every time you use your sewing machine. I know I do. I can’t think of a time when I’ve got out my sewing machine to do some sewing and haven’t used a spool. However, I often run SQL queries that don’t use spools. You see, the data that is consumed by my query is typically in a useful state without a spool. It’s like I can just sew with my cotton despite it not being on a spool! Many of my favourite features in T-SQL do like to use spools though. This looks like a very similar query to before, but includes an OVER clause to return a column telling me the number of rows in my data set. I’ll describe what’s going on in a few paragraphs’ time. So what does a Spool operator actually do? The spool operator consumes a set of data, and stores it in a temporary structure, in the tempdb database. This structure is typically either a Table (ie, a heap), or an Index (ie, a b-tree). If no data is actually needed from it, then it could also be a Row Count spool, which only stores the number of rows that the spool operator consumes. A Window Spool is another option if the data being consumed is tightly linked to windows of data, such as when the ROWS/RANGE clause of the OVER clause is being used. You could maybe think about the type of spool being like whether the cotton is going onto a small bobbin to fit in the base of the sewing machine, or whether it’s a larger spool for the top. A Table or Index Spool is either Eager or Lazy in nature. Eager and Lazy are Logical operators, which talk more about the behaviour, rather than the physical operation. If I’m sewing, I can either be all enthusiastic and get all my cotton onto the spool before I start, or I can do it as I need it. “Lazy” might not the be the best word to describe a person – in the SQL world it describes the idea of either fetching all the rows to build up the whole spool when the operator is called (Eager), or populating the spool only as it’s needed (Lazy). Window Spools are both physical and logical. They’re eager on a per-window basis, but lazy between windows. And when is it needed? The way I see it, spools are needed for two reasons. 1 – When data is going to be needed AGAIN. 2 – When data needs to be kept away from the original source. If you’re someone that writes long stored procedures, you are probably quite aware of the second scenario. I see plenty of stored procedures being written this way – where the query writer populates a temporary table, so that they can make updates to it without risking the original table. SQL does this too. Imagine I’m updating my contact list, and some of my changes move data to later in the book. If I’m not careful, I might update the same row a second time (or even enter an infinite loop, updating it over and over). A spool can make sure that I don’t, by using a copy of the data. This problem is known as the Halloween Effect (not because it’s spooky, but because it was discovered in late October one year). As I’m sure you can imagine, the kind of spool you’d need to protect against the Halloween Effect would be eager, because if you’re only handling one row at a time, then you’re not providing the protection... An eager spool will block the flow of data, waiting until it has fetched all the data before serving it up to the operator that called it. In the query below I’m forcing the Query Optimizer to use an index which would be upset if the Name column values got changed, and we see that before any data is fetched, a spool is created to load the data into. This doesn’t stop the index being maintained, but it does mean that the index is protected from the changes that are being done. There are plenty of times, though, when you need data repeatedly. Consider the query I put above. A simple join, but then counting the number of rows that came through. The way that this has executed (be it ideal or not), is to ask that a Table Spool be populated. That’s the Table Spool operator on the top row. That spool can produce the same set of rows repeatedly. This is the behaviour that we see in the bottom half of the plan. In the bottom half of the plan, we see that the a join is being done between the rows that are being sourced from the spool – one being aggregated and one not – producing the columns that we need for the query. Table v Index When considering whether to use a Table Spool or an Index Spool, the question that the Query Optimizer needs to answer is whether there is sufficient benefit to storing the data in a b-tree. The idea of having data in indexes is great, but of course there is a cost to maintaining them. Here we’re creating a temporary structure for data, and there is a cost associated with populating each row into its correct position according to a b-tree, as opposed to simply adding it to the end of the list of rows in a heap. Using a b-tree could even result in page-splits as the b-tree is populated, so there had better be a reason to use that kind of structure. That all depends on how the data is going to be used in other parts of the plan. If you’ve ever thought that you could use a temporary index for a particular query, well this is it – and the Query Optimizer can do that if it thinks it’s worthwhile. It’s worth noting that just because a Spool is populated using an Index Spool, it can still be fetched using a Table Spool. The details about whether or not a Spool used as a source shows as a Table Spool or an Index Spool is more about whether a Seek predicate is used, rather than on the underlying structure. Recursive CTE I’ve already shown you an example of spooling when the OVER clause is used. You might see them being used whenever you have data that is needed multiple times, and CTEs are quite common here. With the definition of a set of data described in a CTE, if the query writer is leveraging this by referring to the CTE multiple times, and there’s no simplification to be leveraged, a spool could theoretically be used to avoid reapplying the CTE’s logic. Annoyingly, this doesn’t happen. Consider this query, which really looks like it’s using the same data twice. I’m creating a set of data (which is completely deterministic, by the way), and then joining it back to itself. There seems to be no reason why it shouldn’t use a spool for the set described by the CTE, but it doesn’t. On the other hand, if we don’t pull as many columns back, we might see a very different plan. You see, CTEs, like all sub-queries, are simplified out to figure out the best way of executing the whole query. My example is somewhat contrived, and although there are plenty of cases when it’s nice to give the Query Optimizer hints about how to execute queries, it usually doesn’t do a bad job, even without spooling (and you can always use a temporary table). When recursion is used, though, spooling should be expected. Consider what we’re asking for in a recursive CTE. We’re telling the system to construct a set of data using an initial query, and then use set as a source for another query, piping this back into the same set and back around. It’s very much a spool. The analogy of cotton is long gone here, as the idea of having a continual loop of cotton feeding onto a spool and off again doesn’t quite fit, but that’s what we have here. Data is being fed onto the spool, and getting pulled out a second time when the spool is used as a source. (This query is running on AdventureWorks, which has a ManagerID column in HumanResources.Employee, not AdventureWorks2012) The Index Spool operator is sucking rows into it – lazily. It has to be lazy, because at the start, there’s only one row to be had. However, as rows get populated onto the spool, the Table Spool operator on the right can return rows when asked, ending up with more rows (potentially) getting back onto the spool, ready for the next round. (The Assert operator is merely checking to see if we’ve reached the MAXRECURSION point – it vanishes if you use OPTION (MAXRECURSION 0), which you can try yourself if you like). Spools are useful. Don’t lose sight of that. Every time you use temporary tables or table variables in a stored procedure, you’re essentially doing the same – don’t get upset at the Query Optimizer for doing so, even if you think the spool looks like an expensive part of the query. I hope you’re enjoying this T-SQL Tuesday. Why not head over to my post that is hosting it this month to read about some other plan operators? At some point I’ll write a summary post – once I have you should find a comment below pointing at it. @rob_farley

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• Network Access: I can't access 192.168.1.101 from 192.168.1.102.

  - by takpar

  Hi, I'm running Ubuntu 10.04 on my PC with IP 192.168.1.101. every thing work fine, e.g. my web server is running and I can see http://localhost/ or http://192.168.1.101 properly. But the problem is that I cannot see my PC from my laptop at 192.168.1.102 e.g. at my laptop http://192.168.1.101 gives Connection timed out in browser. or trying to telnet on any port leads to: telnet: Unable to connect to remote host: Connection timed out laptop is running a fresh install of Ubuntu as well and there is no setup for firewall stuff in both computers. PS: Both computers can ping each other well. The router is a cicso linksys wireless ADSL modem. Currently, I can connect to FTP server on the Windows running on 192.168.1.102 from 192.168.1.101 without problem. Theses are commands ran on my PC, 192.168.1.101: ifconfig: adp@adp-desktop:~$ ifconfig eth0 Link encap:Ethernet HWaddr 00:26:18:e1:8e:cf inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::226:18ff:fee1:8ecf/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1831935 errors:0 dropped:0 overruns:0 frame:0 TX packets:1493786 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1996855925 (1.9 GB) TX bytes:215288238 (215.2 MB) Interrupt:27 Base address:0xa000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:951742 errors:0 dropped:0 overruns:0 frame:0 TX packets:951742 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:494351095 (494.3 MB) TX bytes:494351095 (494.3 MB) vmnet1 Link encap:Ethernet HWaddr 00:50:46:c0:00:01 inet addr:192.168.91.1 Bcast:192.168.91.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:1/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:50 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) vmnet8 Link encap:Ethernet HWaddr 00:50:46:c0:00:08 inet addr:192.168.156.1 Bcast:192.168.156.255 Mask:255.255.255.0 inet6 addr: fe70::250:56ff:fec0:8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:51 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) port 80 is set to 0.0.0.0 well: adp@adp-desktop:~$ netstat -ln | grep 'LISTEN ' tcp 0 0 127.0.0.1:52815 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4559 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:4369 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:7634 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5269 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5280 0.0.0.0:* LISTEN tcp 0 0 127.0.1.1:7777 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:33601 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:5222 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN tcp6 0 0 :::139 :::* LISTEN tcp6 0 0 ::1:631 :::* LISTEN tcp6 0 0 :::445 :::* LISTEN /etc/hosts.deny is empty: adp@adp-desktop:~$ cat /etc/hosts.deny # /etc/hosts.deny: list of hosts that are _not_ allowed to access the system. # See the manual pages hosts_access(5) and hosts_options(5). # # Example: ALL: some.host.name, .some.domain # ALL EXCEPT in.fingerd: other.host.name, .other.domain # # If you're going to protect the portmapper use the name "portmap" for the # daemon name. Remember that you can only use the keyword "ALL" and IP # addresses (NOT host or domain names) for the portmapper, as well as for # rpc.mountd (the NFS mount daemon). See portmap(8) and rpc.mountd(8) # for further information. # # The PARANOID wildcard matches any host whose name does not match its # address. # # You may wish to enable this to ensure any programs that don't # validate looked up hostnames still leave understandable logs. In past # versions of Debian this has been the default. # ALL: PARANOID netstat -l: adp@adp-desktop:~$ netstat -l Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:52815 *:* LISTEN tcp 0 0 *:hylafax *:* LISTEN tcp 0 0 *:www *:* LISTEN tcp 0 0 *:4369 *:* LISTEN tcp 0 0 localhost:7634 *:* LISTEN tcp 0 0 *:ftp *:* LISTEN tcp 0 0 *:xmpp-server *:* LISTEN tcp 0 0 localhost:ipp *:* LISTEN tcp 0 0 *:smtp *:* LISTEN tcp 0 0 *:5280 *:* LISTEN tcp 0 0 adp-desktop:7777 *:* LISTEN tcp 0 0 *:33601 *:* LISTEN tcp 0 0 *:xmpp-client *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN tcp6 0 0 localhost:ipp [::]:* LISTEN tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN udp 0 0 *:bootpc *:* udp 0 0 *:mdns *:* udp 0 0 *:47467 *:* udp 0 0 192.168.1.10:netbios-ns *:* udp 0 0 192.168.91.1:netbios-ns *:* udp 0 0 192.168.156.:netbios-ns *:* udp 0 0 *:netbios-ns *:* udp 0 0 192.168.1.1:netbios-dgm *:* udp 0 0 192.168.91.:netbios-dgm *:* udp 0 0 192.168.156:netbios-dgm *:* udp 0 0 *:netbios-dgm *:* raw 0 0 *:icmp *:* 7 netstat -rn: adp@adp-desktop:~$ netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.91.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet1 192.168.156.0 0.0.0.0 255.255.255.0 U 0 0 0 vmnet8 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0 commands on the laptop, 192.168.1.102: ifconfig: root@fakeuser-laptop:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:1c:33:a2:31:15 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:21 eth1 Link encap:Ethernet HWaddr 00:2d:d9:3e:1f:6c inet addr:192.168.1.102 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe70::21d:d9ff:fe3e:1f6c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:5681 errors:0 dropped:0 overruns:0 frame:10313 TX packets:6717 errors:6 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4055251 (4.0 MB) TX bytes:779308 (779.3 KB) Interrupt:18 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:206 errors:0 dropped:0 overruns:0 frame:0 TX packets:206 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:15172 (15.1 KB) TX bytes:15172 (15.1 KB) netstat -rn: root@fakeuser-laptop:~# netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth1

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• More Fun With Math

  - by PointsToShare

  More Fun with Math   The runaway student – three different ways of solving one problem Here is a problem I read in a Russian site: A student is running away. He is moving at 1 mph. Pursuing him are a lion, a tiger and his math teacher. The lion is 40 miles behind and moving at 6 mph. The tiger is 28 miles behind and moving at 4 mph. His math teacher is 30 miles behind and moving at 5 mph. Who will catch him first? Analysis Obviously we have a set of three problems. They are all basically the same, but the details are different. The problems are of the same class. Here is a little excursion into computer science. One of the things we strive to do is to create solutions for classes of problems rather than individual problems. In your daily routine, you call it re-usability. Not all classes of problems have such solutions. If a class has a general (re-usable) solution, it is called computable. Otherwise it is unsolvable. Within unsolvable classes, we may still solve individual (some but not all) problems, albeit with different approaches to each. Luckily the vast majority of our daily problems are computable, and the 3 problems of our runaway student belong to a computable class. So, let’s solve for the catch-up time by the math teacher, after all she is the most frightening. She might even make the poor runaway solve this very problem – perish the thought! Method 1 – numerical analysis. At 30 miles and 5 mph, it’ll take her 6 hours to come to where the student was to begin with. But by then the student has advanced by 6 miles. 6 miles require 6/5 hours, but by then the student advanced by another 6/5 of a mile as well. And so on and so forth. So what are we to do? One way is to write code and iterate it until we have solved it. But this is an infinite process so we’ll end up with an infinite loop. So what to do? We’ll use the principles of numerical analysis. Any calculator – your computer included – has a limited number of digits. A double floating point number is good for about 14 digits. Nothing can be computed at a greater accuracy than that. This means that we will not iterate ad infinidum, but rather to the point where 2 consecutive iterations yield the same result. When we do financial computations, we don’t even have to go that far. We stop at the 10th of a penny.  It behooves us here to stop at a 10th of a second (100 milliseconds) and this will how we will avoid an infinite loop. Interestingly this alludes to the Zeno paradoxes of motion – in particular “Achilles and the Tortoise”. Zeno says exactly the same. To catch the tortoise, Achilles must always first come to where the tortoise was, but the tortoise keeps moving – hence Achilles will never catch the tortoise and our math teacher (or lion, or tiger) will never catch the student, or the policeman the thief. Here is my resolution to the paradox. The distance and time in each step are smaller and smaller, so the student will be caught. The only thing that is infinite is the iterative solution. The race is a convergent geometric process so the steps are diminishing, but each step in the solution takes the same amount of effort and time so with an infinite number of steps, we’ll spend an eternity solving it.  This BTW is an original thought that I have never seen before. But I digress. Let’s simply write the code to solve the problem. To make sure that it runs everywhere, I’ll do it in JavaScript. function LongCatchUpTime(D, PV, FV) // D is Distance; PV is Pursuers Velocity; FV is Fugitive’ Velocity {     var t = 0;     var T = 0;     var d = parseFloat(D);     var pv = parseFloat (PV);     var fv = parseFloat (FV);     t = d / pv;     while (t > 0.000001) //a 10th of a second is 1/36,000 of an hour, I used 1/100,000     {         T = T + t;         d = t * fv;         t = d / pv;     }     return T;     } By and large, the higher the Pursuer’s velocity relative to the fugitive, the faster the calculation. Solving this with the 10th of a second limit yields: 7.499999232000001 Method 2 – Geometric Series. Each step in the iteration above is smaller than the next. As you saw, we stopped iterating when the last step was small enough, small enough not to really matter.  When we have a sequence of numbers in which the ratio of each number to its predecessor is fixed we call the sequence geometric. When we are looking at the sum of sequence, we call the sequence of sums series.  Now let’s look at our student and teacher. The teacher runs 5 times faster than the student, so with each iteration the distance between them shrinks to a fifth of what it was before. This is a fixed ratio so we deal with a geometric series.  We normally designate this ratio as q and when q is less than 1 (0 < q < 1) the sum of  + … +  is  – 1) / (q – 1). When q is less than 1, it is easier to use ) / (1 - q). Now, the steps are 6 hours then 6/5 hours then 6/5*5 and so on, so q = 1/5. And the whole series is multiplied by 6. Also because q is less than 1 , 1/  diminishes to 0. So the sum is just  / (1 - q). or 1/ (1 – 1/5) = 1 / (4/5) = 5/4. This times 6 yields 7.5 hours. We can now continue with some algebra and take it back to a simpler formula. This is arduous and I am not going to do it here. Instead let’s do some simpler algebra. Method 3 – Simple Algebra. If the time to capture the fugitive is T and the fugitive travels at 1 mph, then by the time the pursuer catches him he travelled additional T miles. Time is distance divided by speed, so…. (D + T)/V = T  thus D + T = VT  and D = VT – T = (V – 1)T  and T = D/(V – 1) This “strangely” coincides with the solution we just got from the geometric sequence. This is simpler ad faster. Here is the corresponding code. function ShortCatchUpTime(D, PV, FV) {     var d = parseFloat(D);     var pv = parseFloat (PV);     var fv = parseFloat (FV);     return d / (pv - fv); } The code above, for both the iterative solution and the algebraic solution are actually for a larger class of problems.  In our original problem the student’s velocity (speed) is 1 mph. In the code it may be anything as long as it is less than the pursuer’s velocity. As long as PV > FV, the pursuer will catch up. Here is the really general formula: T = D / (PV – FV) Finally, let’s run the program for each of the pursuers.  It could not be worse. I know he’d rather be eaten alive than suffering through yet another math lesson. See the code run? Select  “Catch Up Time” in www.mgsltns.com/games.htm The host is running on Unix, so the link is case sensitive. That’s All Folks

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• Unicast traffic between hosts on a switch leaving the switch by its uplink. Why?

  - by Rich Lafferty

  I have a weird thing happening on our network at my office which I can't quite get my head around. In particular I can't tell if it's a problem with a switch, or a problem with configuration. We have a Cisco SG300-52 switch (sw01) in the top of a rack in our server room, connected to another SG300-28 that acts as our core switch (core01). Both run layer 2 only, our firewalls do routing between VLANs. They have a dozen or so VLANs between them. Gi1 on sw01 is a trunk port connected to gi1 on core01. (Disclosure: There are other switches in our environment but I'm pretty sure I've isolated the problem down to these two. Happy to provide more info if necessary.) The behaviour I'm seeing is limited to one VLAN, vlan 12 -- or, at least, it's not happening on the other ones I checked (It's hard to guarantee the absence of packets), and it is: sw01 is forwarding, to core01, traffic which is between two hosts which are both plugged into sw01. (I noticed this because the IDS in our firewall gave a false positive on traffic which should not reach the firewall.) We noticed this mostly between our two dhcp/dns servers, net01 (10.12.0.10) and net02 (10.12.0.11). net01 is physical hardware and net02 is on a VMware ESX server. net01 is connected to gi44 on sw01 and net02's ESX server to gi11. [net01]----gi44-[sw01]-gi1----gi1-[core01] [net02]----gi11/ Let's see some interfaces! Remember, vlan 12 is the problem vlan. Of the others I explicitly verified that vlan 27 was not affected. Here's the two hosts' ports: esx01 contains net02. sw01#sh run int gi11 interface gigabitethernet11 description esx01 lldp med disable switchport trunk allowed vlan add 5-7,11-13,100 switchport trunk native vlan 27 ! sw01#sh run int gi44 interface gigabitethernet44 description net01-1 lldp med disable switchport mode access switchport access vlan 12 ! Here's the trunk on sw01. sw01#sh run int gi1 interface gigabitethernet1 description "trunk to core01" lldp med disable switchport trunk allowed vlan add 4-7,11-13,27,100 ! And the other end of the trunk on core01. interface gigabitethernet1 description sw01 macro description switch switchport trunk allowed vlan add 2-7,11-16,27,100 ! I have a monitor port on core01, thus: core01#sh run int gi12 interface gigabitethernet12 description "monitor port" port monitor GigabitEthernet 1 ! And the monitor port on core01 sees unicast traffic going between net01 and net02, both of which are on sw01! I've verified this with a monitor port on sw01 that sees the net01-net02 unicast traffic leaving via gi1 too. sw01 knows that both of those hosts are on ports that are not its trunk port: :) ratchet$ arp -a | grep net net02.2ndsiteinc.com (10.12.0.11) at 00:0C:29:1A:66:15 [ether] on eth0 net01.2ndsiteinc.com (10.12.0.10) at 00:11:43:D8:9F:94 [ether] on eth0 sw01#sh mac addr addr 00:0C:29:1A:66:15 Aging time is 300 sec Vlan Mac Address Port Type -------- --------------------- ---------- ---------- 12 00:0c:29:1a:66:15 gi11 dynamic sw01#sh mac addr addr 00:11:43:D8:9F:94 Aging time is 300 sec Vlan Mac Address Port Type -------- --------------------- ---------- ---------- 12 00:11:43:d8:9f:94 gi44 dynamic I also brought up an unused port on sw01 on vlan 12, but the unicast traffic was (as best as I could tell) not coming out that port. So it doesn't look like sw01 is pushing it out all its ports, just the right ports and also gi1! I've verified that sw01 is not filling up its address-table: sw01#sh mac addr count This may take some time. Capacity : 8192 Free : 7983 Used : 208 The full configs for both core01 and sw01 are available: core01, sw01. Finally, versions: sw01#sh ver SW version 1.1.2.0 ( date 12-Nov-2011 time 23:34:26 ) Boot version 1.0.0.4 ( date 08-Apr-2010 time 16:37:57 ) HW version V01 core01#sh ver SW version 1.1.2.0 ( date 12-Nov-2011 time 23:34:26 ) Boot version 1.1.0.6 ( date 11-May-2011 time 18:31:00 ) HW version V01 So my understanding is this: sw01 should take unicast traffic for net01 and send it only out net02's port, and vice versa; none of it should go out sw01's uplink. But core01, receiving traffic on gi1 for a host it knows is on gi1, is right in sending it out all of its ports. (That is: sw01 is misbehaving, but core01 is doing what it should given the circumstances.) My question is: Why is sw01 sending that unicast traffic out its uplink, gi1? (And pre-emptively: yes, I know SG300s leave much to be desired, and yes, we should have spanning-tree enabled, but that's where I'm at right now.)

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• Clean Code Developer & Certification in IT - MSCC 21.09.2013

  It was a very busy weekend this time, and quite some hectic to organise the second meetup on a Saturday for the Mauritius Software Craftsmanship Community (MSCC) but it was absolutely fun. Following, I'm writing a brief summary about the topics we spoke about and the new impulses I got. "What a meetup... I was positively impressed. At the beginning I thought that noone would actually show up but then by the time the room got filled. Lots of conversation, great dialogues and fantastic networking between fresh students, experienced students, experienced employees, and self-employed attendees. That's what community is all about!" Above quote was my first reaction shortly after the gathering. And despite being busy during the weekend and yesterday, I took my time to reflect a little bit on things happened and statements made before writing it here on my blog. Additionally, I was also very curious about possible reactions and blogs from other attendees. Reactions from other craftsmen Let me quickly give you some links and quotes from others first... "Like Jochen posted on facebook, that was indeed a 5+ hours marathon (maybe 4 hours for me but still) … Wohoo! We’re indeed a bunch of crazy geeks who did not realise how time flew as we dived into the myriad discussions that sprouted. Yet in the end everyone was happy (:" -- Ish on MSCC meetup - The marathon (: "And the 4hours spent @ Talking drums bore its fruit..I was doing something I never did before....reading the borrowed book while walking....and though I was not that familiar with things mentionned in the book...I was skimming,scanning & flipping...reading titles...short paragraphs...and I skipped pages till I reached home." -- Yannick on Mauritius Software Craftsmanship 1st Meet-up "Hi Developers, Just wanted to share with you the meetups i attended last Saturday - [...] - The second meetup is the one hosted by Jochen Kirstätter, the MSCC, where the attendees were Craftsman, no woman, this time - all sharing the same passion of being a developer - even though it is on different platforms(Windows - Windows Phone - Linux - Adobe(yes a designer) - .Net) - but we manage to sit at the same table - sharing developer views and experience in the corporate world - also talking about good practice when coding( where Jochen initiated a discussion on Clean Coding ) i could not stay till the end - but from what i have heard - the longer you stay the more fun you have till 1600. Developers in the Facebook grouping i invite you to stay tuned about the various developer communities popping up - where you can come to share and learn good practices, develop the entrepreneurial spirit, and learn and share your passion about technologies" -- Arnaud on Facebook More feedback has been posted on the event directly. So, should I really write more? Wouldn't that spoil the impressions? Starting the day with a surprise Indeed, I was very pleased to stumble over the existence of Mobile Monday Mauritius on LinkedIn, an association about any kind of mobile app development, mobile gadgets and latest smartphones on the market. Despite the Monday in their name they had scheduled their recent meeting on Saturday between 10:00 and 12:00hrs. Wow, what a coincidence! Let's grap the bull by its horns and pay them an introductory visit. As they chose the Ebene Accelerator at the Orange Tower in Ebene it was a no-brainer to leave home a bit earlier and stop by. It was quite an experience and fun to talk to the geeks over there. Really looking forward to organise something together.... Arriving at the venue As the children got a bit uneasy at the MoMo gathering and I didn't want to disturb them too much, we arrived early at Bagatelle. Well, no problems as we went for a decent breakfast at Food Lover's Market. Shortly afterwards we went to our venue location, Talking Drums, and prepared the room for the meeting. We only had to take off a repro-painting of the wall in order to have a decent area for the projector. All went very smooth and my two little ones were of great help. Just in time, our first craftsman Avinash arrived on the spot. And then the waiting started... Luckily, not too long. Bit by bit more and more IT people came to join our meeting. Meanwhile, I used the time to give a brief introduction about the MSCC in general, what we are (hm, maybe I am) trying to achieve and that the recent phase is completely focused on creating more awareness that a community like the MSCC is active here in Mauritius. As soon as we reached some 'critical mass' of about ten people I asked everyone for a short introduction and bio, just in case... Conversation between participants started to kick in and we were actually more networking than having a focus on our topics of the day. Quick updates on latest news and development around the MSCC Finally, Clean Code Developer No matter how the position is actually called, whether it is Software Engineer, Software Developer, Programmer, Architect, or Craftsman, anyone working in IT is facing almost the same obstacles. As for the process of writing software applications there are re-occurring patterns and principles combined with some common exercise and best practices on how to resolve them. Initiated by the must-read book 'Clean Code' by Robert C. Martin (aka Uncle Bob) the concept of the Clean Code Developer (CCD) was born already some years ago. CCD is much likely to traditional martial arts where you create awareness of certain principles and learn how to apply practices to improve your style. The CCD initiative recommends to indicate your level of knowledge and experience with coloured wrist bands - equivalent to the belt colours - for various reasons. Frankly speaking, I think that the biggest advantage here is provided by the obvious recognition of conceptual understanding. For example, take the situation of a team meeting... A member with a higher grade in CCD, say Green grade, sees that there are mainly Red grades to talk to, and adjusts her way of communication to their level of understanding. The choice of words might change as certain elements of CCD are not yet familiar to all team members. So instead of talking in an abstract way which only Green grades could follow the whole scenario comes down to Red grade level. Different story, better results... Similar to learning martial arts, we only covered two grades during this occasion - black and red. Most interestingly, there was quite some positive feedback and lots of questions about the principles and practices of the red grade. And we gathered real-world examples from various craftsman and discussed them. Following the Clean Code Developer Red Grade and some annotations from our meetup: CCD Red Grade - Principles Don't Repeat Yourself - DRY Keep It Simple, Stupid (and Short) - KISS Beware of Optimisations! Favour Composition over Inheritance - FCoI Interestingly most of the attendees already heard about those key words but couldn't really classify or categorize them. It's very similar to a situation in which you do not the particular for a thing and have to describe it to others... until someone tells you the actual name and suddenly all is very simple. CCD Red Grade - Practices Follow the Boy Scouts Rule Root Cause Analysis - RCA Use a Version Control System Apply Simple Refactoring Pattern Reflect Daily Introduction to the principles and practices of Clean Code Developer - here: Red Grade As for the various ToDo's we commonly agreed that the Boy Scout Rule clearly is not limited to software development or IT administration but applies to daily life in general. Same for the root cause analysis, btw. We really had good stories with surprisingly endings and conclusions. A quick check about who is using a version control system brought more drive into the conversation. Not only that we had people that aren't using any VCS at all, we also had the 'classic' approach of backup folders and naming conventions as well as the VCS 'junkie' that has to use multiple systems at a time. Just for the records: Git and GitHub seem to be in favour of some of the attendees. Regarding the daily reflection at the end of the day we came up with an easy solution: Wrap it up as a blog entry! Certifications in IT This is kind of a controversy in IT in general. Is it interesting to go for certifications or are they completely obsolete? What are the possibilities to get certified? What are the options we have in Mauritius? How would certificates stand compared to other educational tracks like Computer Science or Web Design. The ratio between craftsmen with certifications like MCP, MSTS, CCNA or LPI versus the ones without wasn't in favour for the first group but there was a high interest in the topic itself and some were really surprised to hear that exam preparations are completely free available online including temporarily voucher codes for either discounts or completely free exams. Furthermore, we discussed possible options on forming so-called study groups on a specific certificates and organising more frequent meetups in order to learn together. Taking into consideration that we have sponsored access to the video course material of Pluralsight (and now PeepCode as well as TrainSignal), we might give it a try by the end of the year. Current favourites are LPIC Level 1 and one of the Microsoft exams 40-78x. Feedback and ideas for the MSCC The closing conversations and discussions about how the MSCC is recently doing, what are the possibilities and what's (hopefully) going to happen in the future were really fertile and I made a couple of mental bullet points which I'm looking forward to tackle down together with orher craftsmen. Eventually, it might be a good option to elaborate on some issues during our weekly Code & Coffee sessions one Wednesday morning. Active discussion on various IT topics like certifications (LPI, MCP, CCNA, etc) and sharing experience Finally, we made it till the end of the planned time. Well, actually the talk was still on and we continued even after 16:00hrs. Unfortunately, we (the children and I) had to leave for evening activities. My resume of the day... It was great to have 15 craftsmen in one room. There are hundreds of IT geeks out there in Mauritius, and as Mauritius Software Craftsmanship Community we still have a lot of work to do to pass on the message to some more key players and companies. Currently, it seems that we are able to attract a good number of students in Computer Science... but we have a lot more to offer, even or especially for IT people on the job. I'm already looking forward to our next Saturday meetup in the near future. PS: Meetup pictures are courtesy of Nirvan Pagooah. Thanks for sharing...

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• Can Microsoft Build Appliances?

  - by andrewbrust

  Billy Hollis, my Visual Studio Live! colleague and fellow Microsoft Regional Director said recently, and I am paraphrasing, that the computing world, especially on the consumer side, has shifted from one of building hardware and software that makes things possible to do, to building products and technologies that make things easy to do.  Billy crystalized things perfectly, as he often does. In this new world of “easy to do,” Apple has done very well and Microsoft has struggled.  In the old world, customers wanted a Swiss Army Knife, with the most gimmicks and gadgets possible.  In the new world, people want elegantly cutlery.  They may want cake cutters and utility knives too, but they don’t want one device that works for all three tasks.  People don’t want tools, they want utensils.  People don’t want machines.  They want appliances. Microsoft Appliances: They Do Exist Microsoft has built a few appliance-like devices.  I would say XBox 360 is an appliance,  It’s versatile, mind you, but it’s the kind of thing you plug in, turn on and use, as opposed to set-up, tune, and open up to upgrade the internals.  Windows Phone 7 is an appliance too.  It’s a true smartphone, unlike Windows Mobile which was a handheld computer with a radio stack.  Zune is an appliance too, and a nice one.  It hasn’t attained much traction in the market, but that’s probably because the seminal consumer computing appliance -- the iPod – got there so much more quickly. In the embedded world, Mediaroom, Microsoft’s set-top product for the cable industry (used by AT&T U-Verse and others) is an appliance.  So is Microsoft’s Sync technology, used in Ford automobiles.  Even on the enterprise side, Microsoft has an appliance: SQL Server Parallel Data Warehouse Edition (PDW) combines Microsoft software with select OEMs’ server, networking and storage hardware.  You buy the appliance units from the OEMs, plug them in, connect them and go. I would even say that Bing is an appliance.  Not in the hardware sense, mind you.  But from the software perspective, it’s a single-purpose product that you visit or run, use and then move on.  You don’t have to install it (except the iOS and Android native apps where it’s pretty straightforward), you don’t have to customize it, you don’t have to program it.  Basically, you just use it. Microsoft Appliances that Should Exist But Microsoft builds a bunch of things that are not appliances.  Media Center is not an appliance, and it most certainly should be.  Instead, it’s an app that runs on Windows 7.  It runs full-screen and you can use this configuration to conceal the fact that Windows is under it, but eventually something will cause you to abandon that masquerade (like Patch Tuesday). The next version of Windows Home Server won’t, in my opinion, be an appliance either.  Now that the Drive Extender technology is gone, and users can’t just add and remove drives into and from a single storage pool, the product is much more like a IT server and less like an appliance-premised one.  Much has been written about this decision by Microsoft.  I’ll just sum it up in one word: pity. Microsoft doesn’t have anything remotely appliance-like in the tablet category, either.  Until it does, it likely won’t have much market share in that space either.  And of course, the bulk of Microsoft’s product catalog on the business side is geared to enterprise machines and not personal appliances. Appliance DNA: They Gotta Have It. The consumerization of IT is real, because businesspeople are consumers too.  They appreciate the fit and finish of appliances at home, and they increasingly feel entitled to have it at work too.  Secure and reliable push email in a smartphone is necessary, but it isn’t enough.  People want great apps and a pleasurable user experience too.  The full Microsoft Office product is needed at work, but a PC with a keyboard and mouse, or maybe a touch screen that uses a stylus (or requires really small fingers), to run Office isn’t enough either.  People want a flawless touch experience available for the times they want to read and take quick notes.  Until Microsoft realizes this fully and internalizes it, it will suffer defeats in the consumer market and even setbacks in the business market.  Think about how slow the Office upgrade cycle is…now imagine if the next version of Office had a first-class alternate touch UI and consider the possible acceleration in adoption rates. Can Microsoft make the appliance switch?  Can the appliance mentality become pervasive at the company?  Can Microsoft hasten its release cycles dramatically and shed the “some assembly required” paradigm upon which many of its products are based?  Let’s face it, the chances that Microsoft won’t make this transition are significant. But there are also encouraging signs, and they should not be ignored.  The appliances we have already discussed, especially Xbox, Zune and Windows Phone 7, are the most obvious in this regard.  The fact that SQL Server has an appliance SKU now is a more subtle but perhaps also more significant outcome, because that product sits so smack in the middle of Microsoft’s enterprise stack.  Bing is encouraging too, especially given its integrated travel, maps and augmented reality capabilities.  As Bing gains market share, Microsoft has tangible proof that it can transform and win, even when everyone outside the company, and many within it, would bet otherwise. That Great Big Appliance in the Sky Perhaps the most promising (and evolving) proof points toward the appliance mentality, though, are Microsoft’s cloud offerings -- Azure and BPOS/Office 365.  While the cloud does not represent a physical appliance (quite the opposite in fact) its ability to make acquisition, deployment and use of technology simple for the user is absolutely an embodiment of the appliance mentality and spirit.  Azure is primarily a platform as a service offering; it doesn’t just provide infrastructure.  SQL Azure does likewise for databases.  And Office 365 does likewise for SharePoint, Exchange and Lync. You don’t administer, tune and manage servers; instead, you create databases or site collections or mailboxes and start using them. Upgrades come automatically, and it seems like releases will come more frequently.  Fault tolerance and content distribution is just there.  No muss.  No fuss.  You use these services; you don’t have to set them up and think about them.  That’s how appliances work.  To me, these signs point out that Microsoft has the full capability of transforming itself.  But there’s a lot of work ahead.  Microsoft may say they’re “all in” on the cloud, but the majority of the company is still oriented around its old products and models.  There needs to be a wholesale cultural transformation in Redmond.  It can happen, but product management, program management, the field and executive ranks must unify in the effort. So must partners, and even customers.  New leaders must rise up and Microsoft must be able to see itself as a winner.  If Microsoft does this, it could lock-in decades of new success, and be a standard business school case study for doing so.  If not, the company will have missed an opportunity, and may see its undoing.

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• Massive Silverlight Giveaway! DevExpress , Syncfusion, Crypto Obfuscator and SL Spy!

  - by mbcrump

  Oh my, have we grown! Maybe I should change the name to Multiple Silverlight Giveaways. So far, my Silverlight giveaways have been such a success that I’m going to be able to give away more than one Silverlight product every month. Last month, we gave away 3 great products. 1) ComponentOne Silverlight Controls 2)  ComponentOne XAP Optimizer (with obfuscation) and 3) Silverlight Spy. This month, we will give away 4 great Silverlight products and have 4 different winners. This way the Silverlight community can grow with more than just one person winning all the prizes. This month we will be giving away: DevExpress Silverlight Controls – Over 50+ Silverlight Controls Syncfusion User Interface Edition - Create stunning line of business silverlight applications with a wide range of components including a high performance grid, docking manager, chart, gauge, scheduler and much more. Crypto Obfuscator – Works for all .NET including Silverlight/Windows Phone 7. Silverlight Spy – provides a license EVERY month for this giveaway. ----------------------------------------------------------------------------------------------------------------------------------------------------------- Win a FREE developer’s license of one of the products listed above! 4 winners will be announced on April 1st, 2011! To be entered into the contest do the following things: Subscribe to my feed. – Use Google Reader, email or whatever is best for you.  Leave a comment below with a valid email account (I WILL NOT share this info with anyone.) Retweet the following : I just entered to win free #Silverlight controls from @mbcrump . Register here: http://mcrump.me/fTSmB8 ! Don’t change the URL because this will allow me to track the users that Tweet this page. Don’t forget to visit each of the vendors sites because they made this possible. MichaelCrump.Net provides Silverlight Giveaways every month. You can also see the latest giveaway by bookmarking http://giveaways.michaelcrump.net . ---------------------------------------------------------------------------------------------------------------------------------------------------------- DevExpress Silverlight Controls Let’s take a quick look at some of the software that is provided in this giveaway. Before we get started with the Silverlight Controls, here is a couple of links to bookmark for the DevExpress Silverlight Controls: The Live Demos of the Silverlight Controls is located here. Great Video Tutorials of the Silverlight Controls are here. One thing that I liked about the DevExpress is how easy it was to find demos of each control. After you install the controls the following Program Group appears complete with “demos” that include full-source.   So, the first question that you may ask is, “What is included?” Here is the official list below. I wanted to show several of the controls that I think developers will use the most. The Book – Very rich animation between switching pages. Very easy to add your own images and custom text. The Menu – This is another control that just looked great. You can easily add images to the menu items with a few lines of XAML. The Window / Dialog Box – You can use this control to make a very beautiful “Wizard” to help your users navigate between pages. This is useful in setup or installation. Calculator – This would be useful for any type of Banking app. Also a first that I’ve seen from a 3rd party Control company. DatePicker – This controls feels a lot smoother than the one provided by Microsoft. It also provides the ability to “Clear” the selection. Overall the DevExpress Silverlight Controls feature a lot of quality controls that you should check out. You can go ahead and download a trial version of it right now by clicking here. If you win the contest you can simply enter your registration key and continue using the product without reinstalling. Syncfusion User Interface Edition Before we get started with the Syncfusion User Interface Edition, here is a couple of links to bookmark. The Live Demos can be found here. You can download a demo of it now at http://www.syncfusion.com/downloads/evalstart. After you install the Syncfusion, you can view the dashboard to run locally installed samples. You may also download the documentation to your local machine if needed. Since the name of the package is “User Interface Edition”, I decided to share several samples that struck me as “awesome”. Dashboard Gauges – I was very impressed with the various gauges they have included. The digital clock also looks very impressive. Diagram – The diagrams are also very easy to build. In the sample project below you can drag/drop the shapes onto the content pane. More complex lines like the Bezier lines are also easy to create using Syncfusion. Scheduling – Another strong component was the Scheduling with built-in support for Themes. Tools – If all of that wasn’t enough, it also comes with a nice pack of essential tools. Syncfusion has a nice variety of Silverlight Controls that you should check out. You can go ahead and download a trial version of it right now by clicking here. Crypto Obfuscator The following feature set is what is important to me in an Obfuscator since I am a Silverlight/WP7 Developer: And thankfully this is what you get in Crypto Obfuscator. You can download a trial version right now if you want to go ahead and play with it. Let’s spend a few moments taking a look at the application. After you have installed Crypto Obfuscator you will see the following screen: After you click on Assemblies you have the option to add your .XAP file in: I went ahead and loaded my .xap file from a Silverlight Application. At this point, you can simply save your project and hit “Obfuscate” and your done. You don’t have to mess with any of the other settings if you don’t want too. Of course, you can change the settings and add obfuscation rules, watermarks and signing if you wish.  After Obfuscation, it looks like this in .NET Reflector: I was trying to browse through methods and it actually crashed Reflector. This confirms the level of protection the obfuscator is providing. If this were a commercial application that my team built, I would have a huge smile on my face right now. Crypto Obfuscator is a great product and I hope you will spend the time learning more about it. Silverlight Spy Silverlight Spy is a runtime inspector tool that will tell you pretty much everything that is going on with the application. Basically, you give it a URL that contains a Silverlight application and you can explore the element tree, events, xaml and so much more. This has already been reviewed on MichaelCrump.net. _________________________________________________________________________________________ Thanks for reading and don’t forget to leave a comment below in order to win one of the four prizes available! Subscribe to my feed

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• Solaris: What comes next?

  - by alanc

  As you probably know by now, a few months ago, we released Solaris 11 after years of development. That of course means we now need to figure out what comes next - if Solaris 11 is “The First Cloud OS”, then what do we need to make future releases of Solaris be, to be modern and competitive when they're released? So we've been having planning and brainstorming meetings, and I've captured some notes here from just one of those we held a couple weeks ago with a number of the Silicon Valley based engineers. Now before someone sees an idea here and calls their product rep wanting to know what's up, please be warned what follows are rough ideas, and as I'll discuss later, none of them have any committment, schedule, working code, or even plan for integration in any possible future product at this time. (Please don't make me force you to read the full Oracle future product disclaimer here, you should know it by heart already from the front of every Oracle product slide deck.) To start with, we did some background research, looking at ideas from other Oracle groups, and competitive OS'es. We examined what was hot in the technology arena and where the interesting startups were heading. We then looked at Solaris to see where we could apply those ideas. Making Network Admins into Socially Networking Admins We all know an admin who has grumbled about being the only one stuck late at work to fix a problem on the server, or having to work the weekend alone to do scheduled maintenance. But admins are humans (at least most are), and crave companionship and community with their fellow humans. And even when they're alone in the server room, they're never far from a network connection, allowing access to the wide world of wonders on the Internet. Our solution here is not building a new social network - there's enough of those already, and Oracle even has its own Oracle Mix social network already. What we proposed is integrating Solaris features to help engage our system admins with these social networks, building community and bringing them recognition in the workplace, using achievement recognition systems as found in many popular gaming platforms. For instance, if you had a Facebook account, and a group of admin friends there, you could register it with our Social Network Utility For Facebook, and then your friends might see: Alan earned the achievement Critically Patched (April 2012) for patching all his servers. Matt is only at 50% - encourage him to complete this achievement today! To avoid any undue risk of advertising who has unpatched servers that are easier targets for hackers to break into, this information would be tightly protected via Facebook's world-renowned privacy settings to avoid it falling into the wrong hands. A related form of gamification we considered was replacing simple certfications with role-playing-game-style Experience Levels. Instead of just knowing an admin passed a test establishing a given level of competency, these would provide recruiters with a more detailed level of how much real-world experience an admin has. Achievements such as the one above would feed into it, but larger numbers of experience points would be gained by tougher or more critical tasks - such as recovering a down system, or migrating a service to a new platform. (As long as it was an Oracle platform of course - migrating to an HP or IBM platform would cause the admin to lose points with us.) Unfortunately, we couldn't figure out a good way to prevent (if you will) “gaming” the system. For instance, a disgruntled admin might decide to start ignoring warnings from FMA that a part is beginning to fail or skip preventative maintenance, in the hopes that they'd cause a catastrophic failure to earn more points for bolstering their resume as they look for a job elsewhere, and not worrying about the effect on your business of a mission critical server going down. More Z's for ZFS Our suggested new feature for ZFS was inspired by the worlds most successful Z-startup of all time: Zynga. Using the Social Network Utility For Facebook described above, we'd tie it in with ZFS monitoring to help you out when you find yourself in a jam needing more disk space than you have, and can't wait a month to get a purchase order through channels to buy more. Instead with the click of a button you could post to your group: Alan can't find any space in his server farm! Can you help? Friends could loan you some space on their connected servers for a few weeks, knowing that you'd return the favor when needed. ZFS would create a new filesystem for your use on their system, and securely share it with your system using Kerberized NFS. If none of your friends have space, then you could buy temporary use space in small increments at affordable rates right there in Facebook, using your Facebook credits, and then file an expense report later, after the urgent need has passed. Universal Single Sign On One thing all the engineers agreed on was that we still had far too many "Single" sign ons to deal with in our daily work. On the web, every web site used to have its own password database, forcing us to hope we could remember what login name was still available on each site when we signed up, and which unique password we came up with to avoid having to disclose our other passwords to a new site. In recent years, the web services world has finally been reducing the number of logins we have to manage, with many services allowing you to login using your identity from Google, Twitter or Facebook. So we proposed following their lead, introducing PAM modules for web services - no more would you have to type in whatever login name IT assigned and try to remember the password you chose the last time password aging forced you to change it - you'd simply choose which web service you wanted to authenticate against, and would login to your Solaris account upon reciept of a cookie from their identity service. Pinning notes to the cloud We also all noted that we all have our own pile of notes we keep in our daily work - in text files in our home directory, in notebooks we carry around, on white boards in offices and common areas, on sticky notes on our monitors, or on scraps of paper pinned to our bulletin boards. The contents of the notes vary, some are things just for us, some are useful for our groups, some we would share with the world. For instance, when our group moved to a new building a couple years ago, we had a white board in the hallway listing all the NIS & DNS servers, subnets, and other network configuration information we needed to set up our Solaris machines after the move. Similarly, as Solaris 11 was finishing and we were all learning the new network configuration commands, we shared notes in wikis and e-mails with our fellow engineers. Users may also remember one of the popular features of Sun's old BigAdmin site was a section for sharing scripts and tips such as these. Meanwhile, the online "pin board" at Pinterest is taking the web by storm. So we thought, why not mash those up to solve this problem? We proposed a new BigAddPin site where users could “pin” notes, command snippets, configuration information, and so on. For instance, once they had worked out the ideal Automated Installation manifest for their app server, they could pin it up to share with the rest of their group, or choose to make it public as an example for the world. Localized data, such as our group's notes on the servers for our subnet, could be shared only to users connecting from that subnet. And notes that they didn't want others to see at all could be marked private, such as the list of phone numbers to call for late night pizza delivery to the machine room, the birthdays and anniversaries they can never remember but would be sleeping on the couch if they forgot, or the list of automatically generated completely random, impossible to remember root passwords to all their servers. For greater integration with Solaris, we'd put support right into the command shells — redirect output to a pinned note, set your path to include pinned notes as scripts you can run, or bring up your recent shell history and pin a set of commands to save for the next time you need to remember how to do that operation. Location service for Solaris servers A longer term plan would involve convincing the hardware design groups to put GPS locators with wireless transmitters in future server designs. This would help both admins and service personnel trying to find servers in todays massive data centers, and could feed into location presence apps to help show potential customers that while they may not see many Solaris machines on the desktop any more, they are all around. For instance, while walking down Wall Street it might show “There are over 2000 Solaris computers in this block.” [Note: this proposal was made before the recent media coverage of a location service aggregrator app with less noble intentions, and in hindsight, we failed to consider what happens when such data similarly falls into the wrong hands. We certainly wouldn't want our app to be misinterpreted as “There are over $20 million dollars of SPARC servers in this building, waiting for you to steal them.” so it's probably best it was rejected.] Harnessing the power of the GPU for Security Most modern OS'es make use of the widespread availability of high powered GPU hardware in today's computers, with desktop environments requiring 3-D graphics acceleration, whether in Ubuntu Unity, GNOME Shell on Fedora, or Aero Glass on Windows, but we haven't yet made Solaris fully take advantage of this, beyond our basic offering of Compiz on the desktop. Meanwhile, more businesses are interested in increasing security by using biometric authentication, but must also comply with laws in many countries preventing discrimination against employees with physical limations such as missing eyes or fingers, not to mention the lost productivity when employees can't login due to tinted contacts throwing off a retina scan or a paper cut changing their fingerprint appearance until it heals. Fortunately, the two groups considering these problems put their heads together and found a common solution, using 3D technology to enable authentication using the one body part all users are guaranteed to have - pam_phrenology.so, a new PAM module that uses an array USB attached web cams (or just one if the user is willing to spin their chair during login) to take pictures of the users head from all angles, create a 3D model and compare it to the one in the authentication database. While Mythbusters has shown how easy it can be to fool common fingerprint scanners, we have not yet seen any evidence that people can impersonate the shape of another user's cranium, no matter how long they spend beating their head against the wall to reshape it. This could possibly be extended to group users, using modern versions of some of the older phrenological studies, such as giving all users with long grey beards access to the System Architect role, or automatically placing users with pointy spikes in their hair into an easy use mode. Unfortunately, there are still some unsolved technical challenges we haven't figured out how to overcome. Currently, a visit to the hair salon causes your existing authentication to expire, and some users have found that shaving their heads is the only way to avoid bad hair days becoming bad login days. Reaction to these ideas After gathering all our notes on these ideas from the engineering brainstorming meeting, we took them in to present to our management. Unfortunately, most of their reaction cannot be printed here, and they chose not to accept any of these ideas as they were, but they did have some feedback for us to consider as they sent us back to the drawing board. They strongly suggested our ideas would be better presented if we weren't trying to decipher ink blotches that had been smeared by the condensation when we put our pint glasses on the napkins we were taking notes on, and to that end let us know they would not be approving any more engineering offsites in Irish themed pubs on the Friday of a Saint Patrick's Day weekend. (Hopefully they mean that situation specifically and aren't going to deny the funding for travel to this year's X.Org Developer's Conference just because it happens to be in Bavaria and ending on the Friday of the weekend Oktoberfest starts.) They recommended our research techniques could be improved over just sitting around reading blogs and checking our Facebook, Twitter, and Pinterest accounts, such as considering input from alternate viewpoints on topics such as gamification. They also mentioned that Oracle hadn't fully adopted some of Sun's common practices and we might have to try harder to get those to be accepted now that we are one unified company. So as I said at the beginning, don't pester your sales rep just yet for any of these, since they didn't get approved, but if you have better ideas, pass them on and maybe they'll get into our next batch of planning.

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• Why Is Faulty Behaviour In The .NET Framework Not Fixed?

  - by Alois Kraus

  Here is the scenario: You have a Windows Form Application that calls a method via Invoke or BeginInvoke which throws exceptions. Now you want to find out where the error did occur and how the method has been called. Here is the output we do get when we call Begin/EndInvoke or simply Invoke The actual code that was executed was like this:         private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }            [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));   The faulting method is called GenerateError which does throw a NotImplementedException exception and wraps it in a NotSupportedException.           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         } It is clear that the method F2 and F1 did actually throw these exceptions but we do not see them in the call stack. If we directly call the InvokingFunction and catch and print the exception we can find out very easily how we did get into this situation. We see methods F1,F2,GenerateError and InvokingFunction directly in the stack trace and we see that actually two exceptions did occur. Here is for comparison what we get from Invoke/EndInvoke System.NotImplementedException: Inner Exception     StackTrace:    at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)     at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)     at WindowsFormsApplication1.AppForm.InvokingFunction(CallMode mode)     at WindowsFormsApplication1.AppForm.cInvoke_Click(Object sender, EventArgs e)     at System.Windows.Forms.Control.OnClick(EventArgs e)     at System.Windows.Forms.Button.OnClick(EventArgs e) The exception message is kept but the stack starts running from our Invoke call and not from the faulting method F2. We have therefore no clue where this exception did occur! The stack starts running at the method MarshaledInvoke because the exception is rethrown with the throw catchedException which resets the stack trace. That is bad but things are even worse because if previously lets say 5 exceptions did occur .NET will return only the first (innermost) exception. That does mean that we do not only loose the original call stack but all other exceptions and all data contained therein as well. It is a pity that MS does know about this and simply closes this issue as not important. Programmers will play a lot more around with threads than before thanks to TPL, PLINQ that do come with .NET 4. Multithreading is hyped quit a lot in the press and everybody wants to use threads. But if the .NET Framework makes it nearly impossible to track down the easiest UI multithreading issue I have a problem with that. The problem has been reported but obviously not been solved. .NET 4 Beta 2 did not have changed that dreaded GetBaseException call in MarshaledInvoke to return only the innermost exception of the complete exception stack. It is really time to fix this. WPF on the other hand does the right thing and wraps the exceptions inside a TargetInvocationException which makes much more sense. But Not everybody uses WPF for its daily work and Windows forms applications will still be used for a long time. Below is the code to repro the issues shown and how the exceptions can be rendered in a meaningful way. The default Exception.ToString implementation generates a hard to interpret stack if several nested exceptions did occur. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; using System.Globalization; using System.Runtime.CompilerServices;   namespace WindowsFormsApplication1 {     public partial class AppForm : Form     {         enum CallMode         {             Direct = 0,             BeginInvoke = 1,             Invoke = 2         };           public AppForm()         {             InitializeComponent();             Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;             Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);         }           void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e)         {             cOutput.Text = PrintException(e.Exception, 0, null).ToString();         }           private void cDirectUnhandled_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Direct);         }           private void cDirectCall_Click(object sender, EventArgs e)         {             try             {                 InvokingFunction(CallMode.Direct);             }             catch (Exception ex)             {                 cOutput.Text = PrintException(ex, 0, null).ToString();             }         }           private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }           private void cBeginInvokeCall_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.BeginInvoke);         }           [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Direct:                     GenerateError();                     break;                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));                     break;                 case CallMode.BeginInvoke:                     IAsyncResult res = this.BeginInvoke(new MethodInvoker(GenerateError));                     this.EndInvoke(res);                     break;             }         }           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         }           StringBuilder PrintException(Exception ex, int identLevel, StringBuilder sb)         {             StringBuilder builtStr = sb;             if( builtStr == null )                 builtStr = new StringBuilder();               if( ex == null )                 return builtStr;                 WriteLine(builtStr, String.Format("{0}: {1}", ex.GetType().FullName, ex.Message), identLevel);             WriteLine(builtStr, String.Format("StackTrace: {0}", ShortenStack(ex.StackTrace)), identLevel + 1);             builtStr.AppendLine();               return PrintException(ex.InnerException, ++identLevel, builtStr);         }               void WriteLine(StringBuilder sb, string msg, int identLevel)         {             foreach (string trimmedLine in SplitToLines(msg)                                            .Select( (line) => line.Trim()) )             {                 for (int i = 0; i < identLevel; i++)                     sb.Append('\t');                 sb.Append(trimmedLine);                 sb.AppendLine();             }         }           string ShortenStack(string stack)         {             int nonAppFrames = 0;             // Skip stack frames not part of our app but include two foreign frames and skip the rest             // If our stack frame is encountered reset counter to 0             return SplitToLines(stack)                               .Where((line) =>                               {                                   nonAppFrames = line.Contains("WindowsFormsApplication1") ? 0 : nonAppFrames + 1;                                   return nonAppFrames < 3;                               })                              .Select((line) => line)                              .Aggregate("", (current, line) => current + line + Environment.NewLine);         }           static char[] NewLines = Environment.NewLine.ToCharArray();         string[] SplitToLines(string str)         {             return str.Split(NewLines, StringSplitOptions.RemoveEmptyEntries);         }     } }

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• SortedDictionary and SortedList

  - by Simon Cooper

  Apart from Dictionary<TKey, TValue>, there's two other dictionaries in the BCL - SortedDictionary<TKey, TValue> and SortedList<TKey, TValue>. On the face of it, these two classes do the same thing - provide an IDictionary<TKey, TValue> interface where the iterator returns the items sorted by the key. So what's the difference between them, and when should you use one rather than the other? (as in my previous post, I'll assume you have some basic algorithm & datastructure knowledge) SortedDictionary We'll first cover SortedDictionary. This is implemented as a special sort of binary tree called a red-black tree. Essentially, it's a binary tree that uses various constraints on how the nodes of the tree can be arranged to ensure the tree is always roughly balanced (for more gory algorithmical details, see the wikipedia link above). What I'm concerned about in this post is how the .NET SortedDictionary is actually implemented. In .NET 4, behind the scenes, the actual implementation of the tree is delegated to a SortedSet<KeyValuePair<TKey, TValue>>. One example tree might look like this: Each node in the above tree is stored as a separate SortedSet<T>.Node object (remember, in a SortedDictionary, T is instantiated to KeyValuePair<TKey, TValue>): class Node { public bool IsRed; public T Item; public SortedSet<T>.Node Left; public SortedSet<T>.Node Right; } The SortedSet only stores a reference to the root node; all the data in the tree is accessed by traversing the Left and Right node references until you reach the node you're looking for. Each individual node can be physically stored anywhere in memory; what's important is the relationship between the nodes. This is also why there is no constructor to SortedDictionary or SortedSet that takes an integer representing the capacity; there are no internal arrays that need to be created and resized. This may seen trivial, but it's an important distinction between SortedDictionary and SortedList that I'll cover later on. And that's pretty much it; it's a standard red-black tree. Plenty of webpages and datastructure books cover the algorithms behind the tree itself far better than I could. What's interesting is the comparions between SortedDictionary and SortedList, which I'll cover at the end. As a side point, SortedDictionary has existed in the BCL ever since .NET 2. That means that, all through .NET 2, 3, and 3.5, there has been a bona-fide sorted set class in the BCL (called TreeSet). However, it was internal, so it couldn't be used outside System.dll. Only in .NET 4 was this class exposed as SortedSet. SortedList Whereas SortedDictionary didn't use any backing arrays, SortedList does. It is implemented just as the name suggests; two arrays, one containing the keys, and one the values (I've just used random letters for the values): The items in the keys array are always guarenteed to be stored in sorted order, and the value corresponding to each key is stored in the same index as the key in the values array. In this example, the value for key item 5 is 'z', and for key item 8 is 'm'. Whenever an item is inserted or removed from the SortedList, a binary search is run on the keys array to find the correct index, then all the items in the arrays are shifted to accomodate the new or removed item. For example, if the key 3 was removed, a binary search would be run to find the array index the item was at, then everything above that index would be moved down by one: and then if the key/value pair {7, 'f'} was added, a binary search would be run on the keys to find the index to insert the new item, and everything above that index would be moved up to accomodate the new item: If another item was then added, both arrays would be resized (to a length of 10) before the new item was added to the arrays. As you can see, any insertions or removals in the middle of the list require a proportion of the array contents to be moved; an O(n) operation. However, if the insertion or removal is at the end of the array (ie the largest key), then it's only O(log n); the cost of the binary search to determine it does actually need to be added to the end (excluding the occasional O(n) cost of resizing the arrays to fit more items). As a side effect of using backing arrays, SortedList offers IList Keys and Values views that simply use the backing keys or values arrays, as well as various methods utilising the array index of stored items, which SortedDictionary does not (and cannot) offer. The Comparison So, when should you use one and not the other? Well, here's the important differences: Memory usage SortedDictionary and SortedList have got very different memory profiles. SortedDictionary... has a memory overhead of one object instance, a bool, and two references per item. On 64-bit systems, this adds up to ~40 bytes, not including the stored item and the reference to it from the Node object. stores the items in separate objects that can be spread all over the heap. This helps to keep memory fragmentation low, as the individual node objects can be allocated wherever there's a spare 60 bytes. In contrast, SortedList... has no additional overhead per item (only the reference to it in the array entries), however the backing arrays can be significantly larger than you need; every time the arrays are resized they double in size. That means that if you add 513 items to a SortedList, the backing arrays will each have a length of 1024. To conteract this, the TrimExcess method resizes the arrays back down to the actual size needed, or you can simply assign list.Capacity = list.Count. stores its items in a continuous block in memory. If the list stores thousands of items, this can cause significant problems with Large Object Heap memory fragmentation as the array resizes, which SortedDictionary doesn't have. Performance Operations on a SortedDictionary always have O(log n) performance, regardless of where in the collection you're adding or removing items. In contrast, SortedList has O(n) performance when you're altering the middle of the collection. If you're adding or removing from the end (ie the largest item), then performance is O(log n), same as SortedDictionary (in practice, it will likely be slightly faster, due to the array items all being in the same area in memory, also called locality of reference). So, when should you use one and not the other? As always with these sort of things, there are no hard-and-fast rules. But generally, if you: need to access items using their index within the collection are populating the dictionary all at once from sorted data aren't adding or removing keys once it's populated then use a SortedList. But if you: don't know how many items are going to be in the dictionary are populating the dictionary from random, unsorted data are adding & removing items randomly then use a SortedDictionary. The default (again, there's no definite rules on these sort of things!) should be to use SortedDictionary, unless there's a good reason to use SortedList, due to the bad performance of SortedList when altering the middle of the collection.

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• Performance Enhancement in Full-Text Search Query

  - by Calvin Sun

  Ever since its first release, we are continuing consolidating and developing InnoDB Full-Text Search feature. There is one recent improvement that worth blogging about. It is an effort with MySQL Optimizer team that simplifies some common queries’ Query Plans and dramatically shorted the query time. I will describe the issue, our solution and the end result by some performance numbers to demonstrate our efforts in continuing enhancement the Full-Text Search capability. The Issue: As we had discussed in previous Blogs, InnoDB implements Full-Text index as reversed auxiliary tables. The query once parsed will be reinterpreted into several queries into related auxiliary tables and then results are merged and consolidated to come up with the final result. So at the end of the query, we’ll have all matching records on hand, sorted by their ranking or by their Doc IDs. Unfortunately, MySQL’s optimizer and query processing had been initially designed for MyISAM Full-Text index, and sometimes did not fully utilize the complete result package from InnoDB. Here are a couple examples: Case 1: Query result ordered by Rank with only top N results: mysql> SELECT FTS_DOC_ID, MATCH (title, body) AGAINST ('database') AS SCORE FROM articles ORDER BY score DESC LIMIT 1; In this query, user tries to retrieve a single record with highest ranking. It should have a quick answer once we have all the matching documents on hand, especially if there are ranked. However, before this change, MySQL would almost retrieve rankings for almost every row in the table, sort them and them come with the top rank result. This whole retrieve and sort is quite unnecessary given the InnoDB already have the answer. In a real life case, user could have millions of rows, so in the old scheme, it would retrieve millions of rows' ranking and sort them, even if our FTS already found there are two 3 matched rows. Apparently, the million ranking retrieve is done in vain. In above case, it should just ask for 3 matched rows' ranking, all other rows' ranking are 0. If it want the top ranking, then it can just get the first record from our already sorted result. Case 2: Select Count(*) on matching records: mysql> SELECT COUNT(*) FROM articles WHERE MATCH (title,body) AGAINST ('database' IN NATURAL LANGUAGE MODE); In this case, InnoDB search can find matching rows quickly and will have all matching rows. However, before our change, in the old scheme, every row in the table was requested by MySQL one by one, just to check whether its ranking is larger than 0, and later comes up a count. In fact, there is no need for MySQL to fetch all rows, instead InnoDB already had all the matching records. The only thing need is to call an InnoDB API to retrieve the count The difference can be huge. Following query output shows how big the difference can be: mysql> select count(*) from searchindex_inno where match(si_title, si_text) against ('people')  +----------+ | count(*) | +----------+ | 666877 | +----------+ 1 row in set (16 min 17.37 sec) So the query took almost 16 minutes. Let’s see how long the InnoDB can come up the result. In InnoDB, you can obtain extra diagnostic printout by turning on “innodb_ft_enable_diag_print”, this will print out extra query info: Error log: keynr=2, 'people' NL search Total docs: 10954826 Total words: 0 UNION: Searching: 'people' Processing time: 2 secs: row(s) 666877: error: 10 ft_init() ft_init_ext() keynr=2, 'people' NL search Total docs: 10954826 Total words: 0 UNION: Searching: 'people' Processing time: 3 secs: row(s) 666877: error: 10 Output shows it only took InnoDB only 3 seconds to get the result, while the whole query took 16 minutes to finish. So large amount of time has been wasted on the un-needed row fetching. The Solution: The solution is obvious. MySQL can skip some of its steps, optimize its plan and obtain useful information directly from InnoDB. Some of savings from doing this include: 1) Avoid redundant sorting. Since InnoDB already sorted the result according to ranking. MySQL Query Processing layer does not need to sort to get top matching results. 2) Avoid row by row fetching to get the matching count. InnoDB provides all the matching records. All those not in the result list should all have ranking of 0, and no need to be retrieved. And InnoDB has a count of total matching records on hand. No need to recount. 3) Covered index scan. InnoDB results always contains the matching records' Document ID and their ranking. So if only the Document ID and ranking is needed, there is no need to go to user table to fetch the record itself. 4) Narrow the search result early, reduce the user table access. If the user wants to get top N matching records, we do not need to fetch all matching records from user table. We should be able to first select TOP N matching DOC IDs, and then only fetch corresponding records with these Doc IDs. Performance Results and comparison with MyISAM The result by this change is very obvious. I includes six testing result performed by Alexander Rubin just to demonstrate how fast the InnoDB query now becomes when comparing MyISAM Full-Text Search. These tests are base on the English Wikipedia data of 5.4 Million rows and approximately 16G table. The test was performed on a machine with 1 CPU Dual Core, SSD drive, 8G of RAM and InnoDB_buffer_pool is set to 8 GB. Table 1: SELECT with LIMIT CLAUSE mysql> SELECT si_title, match(si_title, si_text) against('family') as rel FROM si WHERE match(si_title, si_text) against('family') ORDER BY rel desc LIMIT 10; InnoDB MyISAM Times Faster Time for the query 1.63 sec 3 min 26.31 sec 127 You can see for this particular query (retrieve top 10 records), InnoDB Full-Text Search is now approximately 127 times faster than MyISAM. Table 2: SELECT COUNT QUERY mysql>select count(*) from si where match(si_title, si_text) against('family‘); +----------+ | count(*) | +----------+ | 293955 | +----------+ InnoDB MyISAM Times Faster Time for the query 1.35 sec 28 min 59.59 sec 1289 In this particular case, where there are 293k matching results, InnoDB took only 1.35 second to get all of them, while take MyISAM almost half an hour, that is about 1289 times faster!. Table 3: SELECT ID with ORDER BY and LIMIT CLAUSE for selected terms mysql> SELECT <ID>, match(si_title, si_text) against(<TERM>) as rel FROM si_<TB> WHERE match(si_title, si_text) against (<TERM>) ORDER BY rel desc LIMIT 10; Term InnoDB (time to execute) MyISAM(time to execute) Times Faster family 0.5 sec 5.05 sec 10.1 family film 0.95 sec 25.39 sec 26.7 Pizza restaurant orange county California 0.93 sec 32.03 sec 34.4 President united states of America 2.5 sec 36.98 sec 14.8 Table 4: SELECT title and text with ORDER BY and LIMIT CLAUSE for selected terms mysql> SELECT <ID>, si_title, si_text, ... as rel FROM si_<TB> WHERE match(si_title, si_text) against (<TERM>) ORDER BY rel desc LIMIT 10; Term InnoDB (time to execute) MyISAM(time to execute) Times Faster family 0.61 sec 41.65 sec 68.3 family film 1.15 sec 47.17 sec 41.0 Pizza restaurant orange county california 1.03 sec 48.2 sec 46.8 President united states of america 2.49 sec 44.61 sec 17.9 Table 5: SELECT ID with ORDER BY and LIMIT CLAUSE for selected terms mysql> SELECT <ID>, match(si_title, si_text) against(<TERM>) as rel  FROM si_<TB> WHERE match(si_title, si_text) against (<TERM>) ORDER BY rel desc LIMIT 10; Term InnoDB (time to execute) MyISAM(time to execute) Times Faster family 0.5 sec 5.05 sec 10.1 family film 0.95 sec 25.39 sec 26.7 Pizza restaurant orange county califormia 0.93 sec 32.03 sec 34.4 President united states of america 2.5 sec 36.98 sec 14.8 Table 6: SELECT COUNT(*) mysql> SELECT count(*) FROM si_<TB> WHERE match(si_title, si_text) against (<TERM>) LIMIT 10; Term InnoDB (time to execute) MyISAM(time to execute) Times Faster family 0.47 sec 82 sec 174.5 family film 0.83 sec 131 sec 157.8 Pizza restaurant orange county califormia 0.74 sec 106 sec 143.2 President united states of america 1.96 sec 220 sec 112.2  Again, table 3 to table 6 all showing InnoDB consistently outperform MyISAM in these queries by a large margin. It becomes obvious the InnoDB has great advantage over MyISAM in handling large data search. Summary: These results demonstrate the great performance we could achieve by making MySQL optimizer and InnoDB Full-Text Search more tightly coupled. I think there are still many cases that InnoDB’s result info have not been fully taken advantage of, which means we still have great room to improve. And we will continuously explore the area, and get more dramatic results for InnoDB full-text searches. Jimmy Yang, September 29, 2012

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• Windows 7 Machine Makes Router Drop -All- Wireless Connections [closed]

  - by Hammer Bro.

  Note: I accidentally originally posted this question over at SuperUser, and I still think the issue is caused by some low-level networking practice of Windows 7, but I think the expertise here would be more apt to figuring it out. Apologies for the cross-post. Some background: My home network consists of my Desktop, a two-month old Windows 7 (x64) machine which is online most frequently (N-spec), as well as three other Windows XP laptops (all G) that only connect every now and then (one for work, one for Netflix, and the other for infrequent regular laptop uses). I used to have a Belkin F5D8236-4 wireless router, and everything worked great. A week ago, however, I found out that the Belkin absolutely in no way would establish a VPN connection, something that has become important for work. So I bought a Netgear WNR3500v2/U/L. The wireless was acting a little sketchy at first for just the Windows 7 machine, but I thought it had something to do with 802.11N and I was in a hurry so I just fished up an ethernet cable and disabled the computer's wireless. It has now become apparent, though, that whenever the Windows 7 machine is connected to the router, all wireless connections become unstable. I was using my work laptop for a solid six hours today with no trouble, having multiple SSH connections open over VPN and streaming internet radio in the background. Then, within two minutes of turning on this Windows 7 box, I had lost all connectivity over the wireless. And I was two feet away from the router. The same sort of thing happens on all of the other laptops -- Netflix can be playing stuff all weekend, but if I come up here and do things on this (W7) computer, the streaming will be dead within ten minutes. So here are my basic observations: If the Windows 7 machine is off, then all connections will have a Signal Strength of Very Good or Excellent and a Speed of 48-54 Mbps for an indefinite amount of time. Shortly after the Windows 7 machine is turned on, all wireless connections will experience a consistent decline in Speed down to 1.0 Mbps, eventually losing their connection entirely. These machines will continue to maintain 70% signal strength, as observed by themselves and router. Once dropped, a wireless connection will have difficulty reconnecting. And, if a connection manages to become established, it will quickly drop off again. The Windows 7 machine itself will continue to function just fine if it's using a wired connection, although it will experience these same issues over the wireless. All of the drivers and firmwares are up to date, and this happened both with the stock Netgear firmware as well as the (current) DD-WRT. What I've tried: Making sure each computer is being assigned a distinct IP. (They are.) Disabling UPnP and Stateful Packet Inspection on the router. Disabling Network Sharing, SSDP Discovery, TCP/IP NetBios Helper and Computer Browser services on the Windows 7 machine. Disabling QoS Packet Scheduler, IPv6, and Link Layer Topology Discovery options on my ethernet controller (leaving only Client for Microsoft Networks, File and Printer Sharing, and IPv4 enabled). What I think: It seems awfully similar to the problems discussed in detail at http://social.msdn.microsoft.com/Forums/en/wsk/thread/1064e397-9d9b-4ae2-bc8e-c8798e591915 (which was both the most relevant and concrete information I could dig up on the internet). I still think that something the Windows 7 IP stack (or just Operating System itself) is doing is giving the router fits. However, I could be wrong, because I have two key differences. One is that most instances of this problem are reported as the entire router dying or restarting, and mine still works just fine over the wired connection. The other is that it's a new router, tested with both the factory firmware and the (I assume) well-maintained DD-WRT project. Even if Windows 7 is still secretly sending IPv6 packets or the TCP Window Scaling implementation that I hear Vista caused some trouble with (even though I've tried my best to disable anything fancy), this router should support those functions. I don't want to get a new or a replacement router unless someone can convince me that this is a defective unit. But the problem seems too specific and predictable by my instincts to be a hardware hiccup. And I don't want to deal with the inevitable problems that always seem to take half a day to resolve when getting a new router, since I'm frantically working (including tomorrow) to complete a project by next week's deadline. Plus, I think in the worst case scenario, I could keep this router connected directly to the modem, disable its wireless entirely, and connect the old Belkin to it directly. That should allow me to still use VPN (although I'll have to plug my work laptop directly into that router), and then maintain wireless connections for all of the other computers. But that feels so wrong to me. Anyone have any ideas what the cause and possible solution could be? Clarifications: The Windows 7 machine is directly connected via an ethernet cable to the router for everything above. But while it is online, all other computers' wireless connections become unusable. It is not an issue of signal strength or interference -- no other devices within scanning range are using Channel 1, and the problem will affect computers that are literally feet away from the router with 95% signal strength.

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• Cloud Computing = Elasticity * Availability

  - by Herve Roggero

  What is cloud computing? Is hosting the same thing as cloud computing? Are you running a cloud if you already use virtual machines? What is the difference between Infrastructure as a Service (IaaS) and a cloud provider? And the list goes on… these questions keep coming up and all try to fundamentally explain what “cloud” means relative to other concepts. At the risk of over simplification, answering these questions becomes simpler once you understand the primary foundations of cloud computing: Elasticity and Availability.   Elasticity The basic value proposition of cloud computing is to pay as you go, and to pay for what you use. This implies that an application can expand and contract on demand, across all its tiers (presentation layer, services, database, security…).  This also implies that application components can grow independently from each other. So if you need more storage for your database, you should be able to grow that tier without affecting, reconfiguring or changing the other tiers. Basically, cloud applications behave like a sponge; when you add water to a sponge, it grows in size; in the application world, the more customers you add, the more it grows. Pure IaaS providers will provide certain benefits, specifically in terms of operating costs, but an IaaS provider will not help you in making your applications elastic; neither will Virtual Machines. The smallest elasticity unit of an IaaS provider and a Virtual Machine environment is a server (physical or virtual). While adding servers in a datacenter helps in achieving scale, it is hardly enough. The application has yet to use this hardware.  If the process of adding computing resources is not transparent to the application, the application is not elastic.   As you can see from the above description, designing for the cloud is not about more servers; it is about designing an application for elasticity regardless of the underlying server farm.   Availability The fact of the matter is that making applications highly available is hard. It requires highly specialized tools and trained staff. On top of it, it's expensive. Many companies are required to run multiple data centers due to high availability requirements. In some organizations, some data centers are simply on standby, waiting to be used in a case of a failover. Other organizations are able to achieve a certain level of success with active/active data centers, in which all available data centers serve incoming user requests. While achieving high availability for services is relatively simple, establishing a highly available database farm is far more complex. In fact it is so complex that many companies establish yearly tests to validate failover procedures.   To a certain degree certain IaaS provides can assist with complex disaster recovery planning and setting up data centers that can achieve successful failover. However the burden is still on the corporation to manage and maintain such an environment, including regular hardware and software upgrades. Cloud computing on the other hand removes most of the disaster recovery requirements by hiding many of the underlying complexities.   Cloud Providers A cloud provider is an infrastructure provider offering additional tools to achieve application elasticity and availability that are not usually available on-premise. For example Microsoft Azure provides a simple configuration screen that makes it possible to run 1 or 100 web sites by clicking a button or two on a screen (simplifying provisioning), and soon SQL Azure will offer Data Federation to allow database sharding (which allows you to scale the database tier seamlessly and automatically). Other cloud providers offer certain features that are not available on-premise as well, such as the Amazon SC3 (Simple Storage Service) which gives you virtually unlimited storage capabilities for simple data stores, which is somewhat equivalent to the Microsoft Azure Table offering (offering a server-independent data storage model). Unlike IaaS providers, cloud providers give you the necessary tools to adopt elasticity as part of your application architecture.    Some cloud providers offer built-in high availability that get you out of the business of configuring clustered solutions, or running multiple data centers. Some cloud providers will give you more control (which puts some of that burden back on the customers' shoulder) and others will tend to make high availability totally transparent. For example, SQL Azure provides high availability automatically which would be very difficult to achieve (and very costly) on premise.   Keep in mind that each cloud provider has its strengths and weaknesses; some are better at achieving transparent scalability and server independence than others.    Not for Everyone Note however that it is up to you to leverage the elasticity capabilities of a cloud provider, as discussed previously; if you build a website that does not need to scale, for which elasticity is not important, then you can use a traditional host provider unless you also need high availability. Leveraging the technologies of cloud providers can be difficult and can become a journey for companies that build their solutions in a scale up fashion. Cloud computing promises to address cost containment and scalability of applications with built-in high availability. If your application does not need to scale or you do not need high availability, then cloud computing may not be for you. In fact, you may pay a premium to run your applications with cloud providers due to the underlying technologies built specifically for scalability and availability requirements. And as such, the cloud is not for everyone.   Consistent Customer Experience, Predictable Cost With all its complexities, buzz and foggy definition, cloud computing boils down to a simple objective: consistent customer experience at a predictable cost.  The objective of a cloud solution is to provide the same user experience to your last customer than the first, while keeping your operating costs directly proportional to the number of customers you have. Making your applications elastic and highly available across all its tiers, with as much automation as possible, achieves the first objective of a consistent customer experience. And the ability to expand and contract the infrastructure footprint of your application dynamically achieves the cost containment objectives.     Herve Roggero is a SQL Azure MVP and co-author of Pro SQL Azure (APress).  He is the co-founder of Blue Syntax Consulting (www.bluesyntax.net), a company focusing on cloud computing technologies helping customers understand and adopt cloud computing technologies. For more information contact herve at hroggero @ bluesyntax.net .

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• Enabling XML-documentation for code contracts

  - by DigiMortal

  One nice feature that code contracts offer is updating of code documentation. If you are using source code documenting features of Visual Studio then code contracts may automate some tasks you otherwise have to implement manually. In this posting I will show you some XML documentation files with documented contracts. I will also explain how this feature works. Enabling XML-documentation in project settings As a first thing let’s enable generating of code documentation under project settings. Open project properties, move to Build page and make check to checkbox called “XML documentation file”. Save project settings and rebuild project. When project is built go to bin/Debug folder and open the XML-file. Here is my XML. <?xml version="1.0"?> <doc>     <assembly>         <name>Eneta.Examples.CodeContracts.Testable</name>     </assembly>     <members>         <member name="T:Eneta.Examples.CodeContracts.Testable.Randomizer">             <summary>             Class for generating random integers in user specified range.             </summary>         </member>         <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.#ctor(Eneta.Examples.CodeContracts.Testable.IRandomGenerator)">             <summary>             Constructor of Randomizer. Initializes Randomizer class.             </summary>             <param name="generator">Instance of random number generator.</param>         </member>         <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.GetRandomFromRangeContracted(System.Int32,System.Int32)">             <summary>             Returns random integer in given range.             </summary>             <param name="min">Minimum value of random integer.</param>             <param name="max">Maximum value of random integer.</param>         </member>     </members> </doc> You can see nothing about code contracts here. Enabling code contracts documentation Code contracts have their own settings and conditions for documentation. Open project properties and move to Code Contracts tab. From “Contract Reference Assembly” dropdown check Build and make check to checkbox “Emit contracts into XML doc file”. And again – save project setting, build the project and move to bin/Debug folder. Now you can see that there are two files for XML-documentation: <assembly name>.XML <assembly name>.old.XML First files is documentation with contracts, second file is original documentation without contracts. Let’s see now what is inside our new XML-documentation file. <?xml version="1.0"?> <doc>   <assembly>     <name>Eneta.Examples.CodeContracts.Testable</name>   </assembly>   <members>     <member name="T:Eneta.Examples.CodeContracts.Testable.Randomizer">       <summary>             Class for generating random integers in user specified range.             </summary>     </member>     <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.#ctor(Eneta.Examples.CodeContracts.Testable.IRandomGenerator)">       <summary>             Constructor of Randomizer. Initializes Randomizer class.             </summary>       <param name="generator">Instance of random number generator.</param>     </member>     <member name="M:Eneta.Examples.CodeContracts.Testable.Randomizer.GetRandomFromRangeContracted(System.Int32,System.Int32)">       <summary>             Returns random integer in given range.             </summary>       <param name="min">Minimum value of random integer.</param>       <param name="max">Maximum value of random integer.</param>       <requires description="Min must be less than max" exception="T:System.ArgumentOutOfRangeException">                 min &lt; max</requires>       <exception cref="T:System.ArgumentOutOfRangeException">                 min &gt;= max</exception>       <ensures description="Return value is out of range">                 Contract.Result&lt;int&gt;() &gt;= min &amp;&amp;                 Contract.Result&lt;int&gt;() &lt;= max</ensures>     </member>   </members> </doc> As you can see then code contracts are pretty well documented. Messages that I provided with code contracts are also available in documentation. If I wrote very good and informative messages then these messages are very useful also in contracts documentation. Code contracts and Sandcastle Sandcastle knows nothing about code contracts by default. There is separate package of file for Sandcastle that is provided you by code contracts installation. You can read from code contracts manual: “Sandcastle (http://www.codeplex.com/Sandcastle) is a freely available tool that generates help les and web sites describing your APIs, based on the XML doc comments in your source code. The CodeContracts install contains a set of les that can be copied over a Sandcastle installation to take advantage of the additional contract information. The produced documentation adds a contract section to methods with declared requires and/or ensures. In order for Sandcastle to produce Contract sections, you need to patch a number of files in its installation. Please refer to the Sandcastle Readme.txt found under Start Menu/CodeContracts/Sandcastle for instructions. A future release of Sandcastle will hopefully support contract sections without the need for this patching step.” Integrating code contracts documentation to Sandcastle will be one of my next postings about code contracts. Conclusion if you are using code documentation then documentation about code contracts can be added to documentation very easily. All you have to do is to enable XML-documentation for contracts and build your project. Later you can use Sandcastle files provided by code contracts installer to integrate contracts documentation to your output documentation package.

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• ASP.NET MVC 3 Hosting :: MVC 2 Strongly Typed HTML Helper and Enhanced Validation Sample

  - by mbridge

  In lue of the off the official release of ASP.NET MVC 2 RTM, I decided I would put together a quick sample of the enhanced HTML.Helpers and validation controls. I am going to use my sample event site where I will have a form so a user can search for information about a certain events. So when the Search page loads the Search action is fired return my strongly typed model. to the view.    1: [HttpGet]    2: public ViewResult Search(): public ViewResult Search()    3: {    4:     IList<EventsModel> result = _eventsService.GetEventList();    5:     var viewModel = new EventSearchModel    6:                         {    7:                             EventList = new SelectList(result, "EventCode","EventName","Select Event")    8:                         };    9:     return View(viewModel);  10: } Nothing special here, although I did want to show how to load up a strongly typed drop down list because that hung me up for a little bit. So to that, I am going to pass back a SelectList to the view and my HTML helper should no how to load this. So lets take a look at the mark up for the view.    1: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master"    2: Inherits="System.Web.Mvc.ViewPage<EventsSample.Models.EventSearchModel>" %>    3:     4: <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">    5:     Search    6: </asp:Content>    7:     8: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">    9:   10:     <h2>Search for Events</h2>  11:   12:     <% using (Html.BeginForm("Search","Events")) {%>  13:         <%= Html.ValidationSummary(true) %>  14:          15:         <fieldset>  16:             <legend>Fields</legend>  17:              18:             <div class="editor-label">  19:                 <%= Html.LabelFor(model => model.EventNumber) %>  20:             </div>  21:             <div class="editor-field">  22:                 <%= Html.TextBoxFor(model => model.EventNumber) %>  23:                 <%= Html.ValidationMessageFor(model => model.EventNumber) %>  24:             </div>  25:              26:             <div class="editor-label">  27:                 <%= Html.LabelFor(model => model.GuestLastName) %>  28:             </div>  29:             <div class="editor-field">  30:                 <%= Html.TextBoxFor(model => model.GuestLastName) %>  31:                 <%= Html.ValidationMessageFor(model => model.GuestLastName) %>  32:             </div>  33:              34:             <div class="editor-label">  35:                 <%= Html.LabelFor(model => model.EventName) %>  36:             </div>  37:             <div class="editor-field">  38:                 <%= Html.DropDownListFor(model => model.EventName, Model.EventList,"Select Event") %>  39:                 <%= Html.ValidationMessageFor(model => model.EventName) %>  40:             </div>  41:              42:             <p>  43:                 <input type="submit" value="Save" />  44:             </p>  45:         </fieldset>  46:   47:     <% } %>  48:   49:     <div>  50:         <%= Html.ActionLink("Back to List", "Index") %>  51:     </div>  52:   53: </asp:Content> A nice feature is the scaffolding that MVC has to generate code. I simply right clicked inside my Search() action, inside the EventsController and selected “Add View” and then I selected my strongly typed object that I wanted to pass to the view and also selected that I wanted the content type be “Edit”. With that the aspx page was completely generated, although I did have to go back in and change the textbox for the Event Names to a drop down list of the names to select from. The new feature with MVC 2 are the strongly typed HTML helpers. So now, my textboxes, drop down list, and validation helpers are all strongly typed to my model.  This features gives you the benefits of intellisense and also makes it easier to debug. “The Gu” has a great post about the feature in case you want more details. The DropDownListFor function to generate the drop down list was a little tricky for me. You first need to use a Lanbda expression to pass in the property you want the selected value assigned to in your model, and then you need to pass in the list directly from the model. Validations To validate the form, you can use the strongly type validation HTML helpers which will inspect your model and return errors if the validation fails. The definitions of these rules are set directly on the Model itself so lets take a look.    1: using System.ComponentModel.DataAnnotations;    2: using System.Web.Mvc;    3:     4: namespace EventsSample.Models    5: {    6:     public class EventSearchModel    7:     {    8:         [Required(ErrorMessage = "Please enter the event number.")]    9:         [RegularExpression(@"\w{6}",  10:             ErrorMessage = "The Event Number must be 6 letters and/or numbers.")]  11:         public string EventNumber { get; set; }  12:   13:         [Required(ErrorMessage = "Please enter the guest's last name.")]  14:         [RegularExpression(@"^[A-Za-zÀ-ÖØ-öø-ÿ1-9 '\-\.]{1,22}$",  15:             ErrorMessage = "The gueest's last name must 1 to 20 characters.")]  16:         public string GuestLastName { get; set; }  17:   18:         public string EventName { get; set; }  19:         public SelectList EventList { get; set; }  20:     }  21: } Pretty cool! Okay, the only thing left to do is perform the validation in the POST action.    1: [HttpPost]    2: public ViewResult Search(EventSearchModel eventSearchModel)    3: {    4:     if (ModelState.IsValid) return View("SearchResults");    5:     else    6:     {    7:          IList<EventsModel> result = _eventsService.GetEventList();    8:         eventSearchModel.EventList = new SelectList(result, "EVentCode","EventName");   9:   10:         return View(eventSearchModel);  11:     }  12: }  13:     } If the form entries are valid, here I am simply displaying the SearchResult, but in a real world sample I would also go out get the results first. You get the idea though. In my case, when the form is not valid, I also had to reload my SelectList with the event names before I loaded the page again. Remember this is MVC, no _VieState here :) So that’s it. Now my form is validating the data and when it fails it looks like this.

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• Changing CSS with jQuery syntax in Silverlight using jLight

  - by Timmy Kokke

  Lately I’ve ran into situations where I had to change elements or had to request a value in the DOM from Silverlight. jLight, which was introduced in an earlier article, can help with that. jQuery offers great ways to change CSS during runtime. Silverlight can access the DOM, but it isn’t as easy as jQuery. All examples shown in this article can be looked at in this online demo. The code can be downloaded here.   Part 1: The easy stuff Selecting and changing properties is pretty straight forward. Setting the text color in all <B> </B> elements can be done using the following code:   jQuery.Select("b").Css("color", "red");   The Css() method is an extension method on jQueryObject which is return by the jQuery.Select() method. The Css() method takes to parameters. The first is the Css style property. All properties used in Css can be entered in this string. The second parameter is the value you want to give the property. In this case the property is “color” and it is changed to “red”. To specify which element you want to select you can add a :selector parameter to the Select() method as shown in the next example.   jQuery.Select("b:first").Css("font-family", "sans-serif");   The “:first” pseudo-class selector selects only the first element. This example changes the “font-family” property of the first <B></B> element to “sans-serif”. To make use of intellisense in Visual Studio I’ve added a extension methods to help with the pseudo-classes. In the example below the “font-weight” of every “Even” <LI></LI> is set to “bold”.   jQuery.Select("li".Even()).Css("font-weight", "bold");   Because the Css() extension method returns a jQueryObject it is possible to chain calls to Css(). The following example show setting the “color”, “background-color” and the “font-size” of all headers in one go.   jQuery.Select(":header").Css("color", "#12FF70") .Css("background-color", "yellow") .Css("font-size", "25px");   Part 2: More complex stuff In only a few cases you need to change only one style property. More often you want to change an entire set op style properties all in one go.  You could chain a lot of Css() methods together. A better way is to add a class to a stylesheet and define all properties in there. With the AddClass() method you can set a style class to a set of elements. This example shows how to add the “demostyle” class to all <B></B> in the document.   jQuery.Select("b").AddClass("demostyle");   Removing the class works in the same way:   jQuery.Select("b").RemoveClass("demostyle");   jLight is build for interacting with to the DOM from Silverlight using jQuery. A jQueryObjectCss object can be used to define different sets of style properties in Silverlight. The over 60 most common Css style properties are defined in the jQueryObjectCss class. A string indexer can be used to access all style properties ( CssObject1[“background-color”] equals CssObject1.BackgroundColor). In the code below, two jQueryObjectCss objects are defined and instantiated.   private jQueryObjectCss CssObject1; private jQueryObjectCss CssObject2;   public Demo2() { CssObject1 = new jQueryObjectCss { BackgroundColor = "Lime", Color="Black", FontSize = "12pt", FontFamily = "sans-serif", FontWeight = "bold", MarginLeft = 150, LineHeight = "28px", Border = "Solid 1px #880000" }; CssObject2 = new jQueryObjectCss { FontStyle = "Italic", FontSize = "48", Color = "#225522" }; InitializeComponent(); }   Now instead of chaining to set all different properties you can just pass one of the jQueryObjectCss objects to the Css() method. In this case all <LI></LI> elements are set to match this object.   jQuery.Select("li").Css(CssObject1); When using the jQueryObjectCss objects chaining is still possible. In the following example all headers are given a blue backgroundcolor and the last is set to match CssObject2.   jQuery.Select(":header").Css(new jQueryObjectCss{BackgroundColor = "Blue"}) .Eq(-1).Css(CssObject2);   Part 3: The fun stuff Having Silverlight call JavaScript and than having JavaScript to call Silverlight requires a lot of plumbing code. Everything has to be registered and strings are passed back and forth to execute the JavaScript. jLight makes this kind of stuff so easy, it becomes fun to use. In a lot of situations jQuery can call a function to decide what to do, setting a style class based on complex expressions for example. jLight can do the same, but the callback methods are defined in Silverlight. This example calls the function() method for each <LI></LI> element. The callback method has to take a jQueryObject, an integer and a string as parameters. In this case jLight differs a bit from the actual jQuery implementation. jQuery uses only the index and the className parameters. A jQueryObject is added to make it simpler to access the attributes and properties of the element. If the text of the listitem starts with a ‘D’ or an ‘M’ the class is set. Otherwise null is returned and nothing happens.   private void button1_Click(object sender, RoutedEventArgs e) { jQuery.Select("li").AddClass(function); }   private string function(jQueryObject obj, int index, string className) { if (obj.Text[0] == 'D' || obj.Text[0] == 'M') return "demostyle"; return null; }   The last thing I would like to demonstrate uses even more Silverlight and less jLight, but demonstrates the power of the combination. Animating a style property using a Storyboard with easing functions. First a dependency property is defined. In this case it is a double named Intensity. By handling the changed event the color is set using jQuery.   public double Intensity { get { return (double)GetValue(IntensityProperty); } set { SetValue(IntensityProperty, value); } }   public static readonly DependencyProperty IntensityProperty = DependencyProperty.Register("Intensity", typeof(double), typeof(Demo3), new PropertyMetadata(0.0, IntensityChanged));   private static void IntensityChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var i = (byte)(double)e.NewValue; jQuery.Select("span").Css("color", string.Format("#{0:X2}{0:X2}{0:X2}", i)); }   An animation has to be created. This code defines a Storyboard with one keyframe that uses a bounce ease as an easing function. The animation is set to target the Intensity dependency property defined earlier.   private Storyboard CreateAnimation(double value) { Storyboard storyboard = new Storyboard(); var da = new DoubleAnimationUsingKeyFrames(); var d = new EasingDoubleKeyFrame { EasingFunction = new BounceEase(), KeyTime = KeyTime.FromTimeSpan(TimeSpan.FromSeconds(1.0)), Value = value }; da.KeyFrames.Add(d); Storyboard.SetTarget(da, this); Storyboard.SetTargetProperty(da, new PropertyPath(Demo3.IntensityProperty)); storyboard.Children.Add(da); return storyboard; }   Initially the Intensity is set to 128 which results in a gray color. When one of the buttons is pressed, a new animation is created an played. One to animate to black, and one to animate to white.   public Demo3() { InitializeComponent(); Intensity = 128; }   private void button2_Click(object sender, RoutedEventArgs e) { CreateAnimation(255).Begin(); }   private void button3_Click(object sender, RoutedEventArgs e) { CreateAnimation(0).Begin(); }   Conclusion As you can see jLight can make the life of a Silverlight developer a lot easier when accessing the DOM. Almost all jQuery functions that are defined in jLight use the same constructions as described above. I’ve tried to stay as close as possible to the real jQuery. Having JavaScript perform callbacks to Silverlight using jLight will be described in more detail in a future tutorial about AJAX or eventing.

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• Anatomy of a .NET Assembly - CLR metadata 1

  - by Simon Cooper

  Before we look at the bytes comprising the CLR-specific data inside an assembly, we first need to understand the logical format of the metadata (For this post I only be looking at simple pure-IL assemblies; mixed-mode assemblies & other things complicates things quite a bit). Metadata streams Most of the CLR-specific data inside an assembly is inside one of 5 streams, which are analogous to the sections in a PE file. The name of each section in a PE file starts with a ., and the name of each stream in the CLR metadata starts with a #. All but one of the streams are heaps, which store unstructured binary data. The predefined streams are: #~ Also called the metadata stream, this stream stores all the information on the types, methods, fields, properties and events in the assembly. Unlike the other streams, the metadata stream has predefined contents & structure. #Strings This heap is where all the namespace, type & member names are stored. It is referenced extensively from the #~ stream, as we'll be looking at later. #US Also known as the user string heap, this stream stores all the strings used in code directly. All the strings you embed in your source code end up in here. This stream is only referenced from method bodies. #GUID This heap exclusively stores GUIDs used throughout the assembly. #Blob This heap is for storing pure binary data - method signatures, generic instantiations, that sort of thing. Items inside the heaps (#Strings, #US, #GUID and #Blob) are indexed using a simple binary offset from the start of the heap. At that offset is a coded integer giving the length of that item, then the item's bytes immediately follow. The #GUID stream is slightly different, in that GUIDs are all 16 bytes long, so a length isn't required. Metadata tables The #~ stream contains all the assembly metadata. The metadata is organised into 45 tables, which are binary arrays of predefined structures containing information on various aspects of the metadata. Each entry in a table is called a row, and the rows are simply concatentated together in the file on disk. For example, each row in the TypeRef table contains: A reference to where the type is defined (most of the time, a row in the AssemblyRef table). An offset into the #Strings heap with the name of the type An offset into the #Strings heap with the namespace of the type. in that order. The important tables are (with their table number in hex): 0x2: TypeDef 0x4: FieldDef 0x6: MethodDef 0x14: EventDef 0x17: PropertyDef Contains basic information on all the types, fields, methods, events and properties defined in the assembly. 0x1: TypeRef The details of all the referenced types defined in other assemblies. 0xa: MemberRef The details of all the referenced members of types defined in other assemblies. 0x9: InterfaceImpl Links the types defined in the assembly with the interfaces that type implements. 0xc: CustomAttribute Contains information on all the attributes applied to elements in this assembly, from method parameters to the assembly itself. 0x18: MethodSemantics Links properties and events with the methods that comprise the get/set or add/remove methods of the property or method. 0x1b: TypeSpec 0x2b: MethodSpec These tables provide instantiations of generic types and methods for each usage within the assembly. There are several ways to reference a single row within a table. The simplest is to simply specify the 1-based row index (RID). The indexes are 1-based so a value of 0 can represent 'null'. In this case, which table the row index refers to is inferred from the context. If the table can't be determined from the context, then a particular row is specified using a token. This is a 4-byte value with the most significant byte specifying the table, and the other 3 specifying the 1-based RID within that table. This is generally how a metadata table row is referenced from the instruction stream in method bodies. The third way is to use a coded token, which we will look at in the next post. So, back to the bytes Now we've got a rough idea of how the metadata is logically arranged, we can now look at the bytes comprising the start of the CLR data within an assembly: The first 8 bytes of the .text section are used by the CLR loader stub. After that, the CLR-specific data starts with the CLI header. I've highlighted the important bytes in the diagram. In order, they are: The size of the header. As the header is a fixed size, this is always 0x48. The CLR major version. This is always 2, even for .NET 4 assemblies. The CLR minor version. This is always 5, even for .NET 4 assemblies, and seems to be ignored by the runtime. The RVA and size of the metadata header. In the diagram, the RVA 0x20e4 corresponds to the file offset 0x2e4 Various flags specifying if this assembly is pure-IL, whether it is strong name signed, and whether it should be run as 32-bit (this is how the CLR differentiates between x86 and AnyCPU assemblies). A token pointing to the entrypoint of the assembly. In this case, 06 (the last byte) refers to the MethodDef table, and 01 00 00 refers to to the first row in that table. (after a gap) RVA of the strong name signature hash, which comes straight after the CLI header. The RVA 0x2050 corresponds to file offset 0x250. The rest of the CLI header is mainly used in mixed-mode assemblies, and so is zeroed in this pure-IL assembly. After the CLI header comes the strong name hash, which is a SHA-1 hash of the assembly using the strong name key. After that comes the bodies of all the methods in the assembly concatentated together. Each method body starts off with a header, which I'll be looking at later. As you can see, this is a very small assembly with only 2 methods (an instance constructor and a Main method). After that, near the end of the .text section, comes the metadata, containing a metadata header and the 5 streams discussed above. We'll be looking at this in the next post. Conclusion The CLI header data doesn't have much to it, but we've covered some concepts that will be important in later posts - the logical structure of the CLR metadata and the overall layout of CLR data within the .text section. Next, I'll have a look at the contents of the #~ stream, and how the table data is arranged on disk.

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• More Fun with C# Iterators and Generators

  - by James Michael Hare

  In my last post, I talked quite a bit about iterators and how they can be really powerful tools for filtering a list of items down to a subset of items.  This had both pros and cons over returning a full collection, which, in summary, were:   Pros: If traversal is only partial, does not have to visit rest of collection. If evaluation method is costly, only incurs that cost on elements visited. Adds little to no garbage collection pressure.    Cons: Very slight performance impact if you know caller will always consume all items in collection. And as we saw in the last post, that con for the cost was very, very small and only really became evident on very tight loops consuming very large lists completely.    One of the key items to note, though, is the garbage!  In the traditional (return a new collection) method, if you have a 1,000,000 element collection, and wish to transform or filter it in some way, you have to allocate space for that copy of the collection.  That is, say you have a collection of 1,000,000 items and you want to double every item in the collection.  Well, that means you have to allocate a collection to hold those 1,000,000 items to return, which is a lot especially if you are just going to use it once and toss it.   Iterators, though, don't have this problem.  Each time you visit the node, it would return the doubled value of the node (in this example) and not allocate a second collection of 1,000,000 doubled items.  Do you see the distinction?  In both cases, we're consuming 1,000,000 items.  But in one case we pass back each doubled item which is just an int (for example's sake) on the stack and in the other case, we allocate a list containing 1,000,000 items which then must be garbage collected.   So iterators in C# are pretty cool, eh?  Well, here's one more thing a C# iterator can do that a traditional "return a new collection" transformation can't!   It can return **unbounded** collections!   I know, I know, that smells a lot like an infinite loop, eh?  Yes and no.  Basically, you're relying on the caller to put the bounds on the list, and as long as the caller doesn't you keep going.  Consider this example:   public static class Fibonacci {     // returns the infinite fibonacci sequence     public static IEnumerable<int> Sequence()     {         int iteration = 0;         int first = 1;         int second = 1;         int current = 0;         while (true)         {             if (iteration++ < 2)             {                 current = 1;             }             else             {                 current = first + second;                 second = first;                 first = current;             }             yield return current;         }     } }   Whoa, you say!  Yes, that's an infinite loop!  What the heck is going on there?  Yes, that was intentional.  Would it be better to have a fibonacci sequence that returns only a specific number of items?  Perhaps, but that wouldn't give you the power to defer the execution to the caller.   The beauty of this function is it is as infinite as the sequence itself!  The fibonacci sequence is unbounded, and so is this method.  It will continue to return fibonacci numbers for as long as you ask for them.  Now that's not something you can do with a traditional method that would return a collection of ints representing each number.  In that case you would eventually run out of memory as you got to higher and higher numbers.  This method, though, never runs out of memory.   Now, that said, you do have to know when you use it that it is an infinite collection and bound it appropriately.  Fortunately, Linq provides a lot of these extension methods for you!   Let's say you only want the first 10 fibonacci numbers:       foreach(var fib in Fibonacci.Sequence().Take(10))     {         Console.WriteLine(fib);     }   Or let's say you only want the fibonacci numbers that are less than 100:       foreach(var fib in Fibonacci.Sequence().TakeWhile(f => f < 100))     {         Console.WriteLine(fib);     }   So, you see, one of the nice things about iterators is their power to work with virtually any size (even infinite) collections without adding the garbage collection overhead of making new collections.    You can also do fun things like this to make a more "fluent" interface for for loops:   // A set of integer generator extension methods public static class IntExtensions {     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> Every(this int start)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; ++i)         {             yield return i;         }     }     // Begins counting to infinity by the given step value, use To() to     public static IEnumerable<int> Every(this int start, int byEvery)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; i += byEvery)         {             yield return i;         }     }     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> To(this int start, int end)     {         for (var i = start; i <= end; ++i)         {             yield return i;         }     }     // Ranges the count by specifying the upper range of the count.     public static IEnumerable<int> To(this IEnumerable<int> collection, int end)     {         return collection.TakeWhile(item => item <= end);     } }   Note that there are two versions of each method.  One that starts with an int and one that starts with an IEnumerable<int>.  This is to allow more power in chaining from either an existing collection or from an int.  This lets you do things like:   // count from 1 to 30 foreach(var i in 1.To(30)) {     Console.WriteLine(i); }     // count from 1 to 10 by 2s foreach(var i in 0.Every(2).To(10)) {     Console.WriteLine(i); }     // or, if you want an infinite sequence counting by 5s until something inside breaks you out... foreach(var i in 0.Every(5)) {     if (someCondition)     {         break;     }     ... }     Yes, those are kinda play functions and not particularly useful, but they show some of the power of generators and extension methods to form a fluid interface.   So what do you think?  What are some of your favorite generators and iterators?

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• The Java Specialist: An Interview with Java Champion Heinz Kabutz

  - by Janice J. Heiss

  Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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• The Java Specialist: An Interview with Java Champion Heinz Kabutz

  - by Janice J. Heiss

  Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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• Introduction to LinqPad Driver for StreamInsight 2.1

  - by Roman Schindlauer

  We are announcing the availability of the LinqPad driver for StreamInsight 2.1. The purpose of this blog post is to offer a quick introduction into the new features that we added to the StreamInsight LinqPad driver. We’ll show you how to connect to a remote server, how to inspect the entities present of that server, how to compose on top of them and how to manage their lifetime. Installing the driver Info on how to install the driver can be found in an earlier blog post here. Establishing connections As you click on the “Add Connection” link in the left pane you will notice that now it’s possible to build the data context automatically. The new driver appears as an option in the upper list, and if you pick it you will open a connection dialog that lets you connect to a remote StreamInsight server. The connection dialog lets you specify the address of the remote server. You will notice that it’s possible to pick up the binding information from the configuration file of the LinqPad application (which is normally in the same folder as LinqPad.exe and is called LinqPad.exe.config). In order for the context to be generated you need to pick an application from the server. The control is editable hence you can create a new application if you don’t want to make changes to an existing application. If you choose a new application name you will be prompted for confirmation before this gets created. Once you click OK the connection is created and you can start issuing queries against the remote server. If there’s any connectivity error the connection is marked with a red X and you can see the error message informing you what went wrong (i.e., the remote server could not be reached etc.). The context for remote servers Let’s take a look at what happens after we are connected successfully. Every LinqPad query runs inside a context – think of it as a class that wraps all the code that you’re writing. If you’re connecting to a live server the context will contain the following: The application object itself. All entities present in this application (sources, sinks, subjects and processes). The picture below shows a snapshot of the left pane of LinqPad after a successful connection. Every entity on the server has a different icon which will allow users to figure out its purpose. You will also notice that some entities have a string in parentheses following the name. It should be interpreted as such: the first name is the name of the property of the context class and the second name is the name of the entity as it exists on the server. Not all valid entity names are valid identifier names so in cases where we had to make a transformation you see both. Note also that as you hover over the entities you get IntelliSense with their types – more on that later. Remoting is not supported As you play with the entities exposed by the context you will notice that you can’t read and write directly to/from them. If for instance you’re trying to dump the content of an entity you will get an error message telling you that in the current version remoting is not supported. This is because the entity lives on the remote server and dumping its content means reading the events produced by this entity into the local process. ObservableSource.Dump(); Will yield the following error: Reading from a remote 'System.Reactive.Linq.IQbservable`1[System.Int32]' is not supported. Use the 'Microsoft.ComplexEventProcessing.Linq.RemoteProvider.Bind' method to read from the source using a remote observer. This basically tells you that you can call the Bind() method to direct the output of this source to a sink that has to be defined on the remote machine as well. You can’t bring the results to the LinqPad window unless you write code specifically for that. Compose queries You may ask – what's the purpose of all that? After all the same information is present in the EventFlowDebugger, why bother with showing it in LinqPad? First of all, What gets exposed in LinqPad is not what you see in the debugger. In LinqPad we have a property on the context class for every entity that lives on the server. Because LinqPad offers IntelliSense we in fact have much more information about the entity, and more importantly we can compose with that entity very easily. For example, let’s say that this code creates an entity: using (var server = Server.Connect(...)) {     var a = server.CreateApplication("WhiteFish");     var src = a         .DefineObservable<int>(() => Observable.Range(0, 3))         .Deploy("ObservableSource"); If later we want to compose with the source we have to fetch it and then we can bind something to     a.GetObservable<int>("ObservableSource)").Bind(... This means that we had to know a bunch of things about this: that it’s a source, that it’s an observable, it produces a result with payload Int32 and it’s named “ObservableSource”. Only the second and last bits of information are present in the debugger, by the way. As you type in the query window you see that all the entities are present, you get IntelliSense support for them and it’s much easier to make sense of what’s available. Let’s look at a scenario where composition is plausible. With the new programming model it’s possible to create “cold” sources that are parameterized. There was a way to accomplish that even in the previous version by passing parameters to the adapters, but this time it’s much more elegant because the expression declares what parameters are required. Say that we hover the mouse over the ThrottledSource source – we will see that its type is Func<int, int, IQbservable<int>> - this in effect means that we need to pass two int parameters before we can get a source that produces events, and the type for those events is int – in the particular case of my example I had the source produce a range of integers and the two parameters were the start and end of the range. So we see how a developer can create a source that is not running yet. Then someone else (e.g. an administrator) can pass whatever parameters appropriate and run the process. Proxy Types Here’s an interesting scenario – what if someone created a source on a server but they forgot to tell you what type they used. Worse yet, they might have used an anonymous type and even though they can refer to it by name you can’t figure out how to use that type. Let’s walk through an example that shows how you can compose against types you don’t need to have the definition of. This is how we can create a source that returns an anonymous type: Application.DefineObservable(() => Observable.Range(1, 10).Select(i => new { I = i })).Deploy("O1"); Now if we refresh the connection we can see the new source named O1 appear in the list. But what’s more important is that we now have a type to work with. So we can compose a query that refers to the anonymous type. var threshold = new StreamInsightDynamicDriver.TypeProxies.AnonymousType1_0<int>(5); var filter = from i in O1              where i > threshold              select i; filter.Deploy("O2"); You will notice that the anonymous type defined with this statement: new { I = i } can now be manipulated by a client that does not have access to it because the LinqPad driver has generated another type in its stead, named StreamInsightDynamicDriver.TypeProxies.AnonymousType1_0. This type has all the properties and fields of the type defined on the server, except in this case we can instantiate values and use it to compose more queries. It is worth noting that the same thing works for types that are not anonymous – the test is if the LinqPad driver can resolve the type or not. If it’s not possible then a new type will be generated that approximates the type that exists on the server. Control metadata In addition to composing processes on top of the existing entities we can do other useful things. We can delete them – nothing new here as we simply access the entities through the Entities collection of the application class. Here is where having their real name in parentheses comes handy. There’s another way to find out what’s behind a property – dump its expression. The first line in the output tells us what’s the name of the entity used to build this property in the context. Runtime information So let’s create a process to see what happens. We can bind a source to a sink and run the resulting process. If you right click on the connection you can refresh it and see the process present in the list of entities. Then you can drag the process to the query window and see that you can have access to process object in the Processes collection of the application. You can then manipulate the process (delete it, read its diagnostic view etc.). Regards, The StreamInsight Team

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• ANTS Memory Profiler 7.0

  - by James Michael Hare

  I had always been a fan of ANTS products (Reflector is absolutely invaluable, and their performance profiler is great as well – very easy to use!), so I was curious to see what the ANTS Memory Profiler could show me. Background While a performance profiler will track how much time is typically spent in each unit of code, a memory profiler gives you much more detail on how and where your memory is being consumed and released in a program. As an example, I’d been working on a data access layer at work to call a market data web service.  This web service would take a list of symbols to quote and would return back the quote data.  To help consolidate the thousands of web requests per second we get and reduce load on the web services, we implemented a 5-second cache of quote data.  Not quite long enough to where customers will typically notice a quote go “stale”, but just long enough to be able to collapse multiple quote requests for the same symbol in a short period of time. A 5-second cache may not sound like much, but it actually pays off by saving us roughly 42% of our web service calls, while still providing relatively up-to-date information.  The question is whether or not the extra memory involved in maintaining the cache was worth it, so I decided to fire up the ANTS Memory Profiler and take a look at memory usage. First Impressions The main thing I’ve always loved about the ANTS tools is their ease of use.  Pretty much everything is right there in front of you in a way that makes it easy for you to find what you need with little digging required.  I’ve worked with other, older profilers before (that shall remain nameless other than to hint it was created by a very large chip maker) where it was a mind boggling experience to figure out how to do simple tasks. Not so with AMP.  The opening dialog is very straightforward.  You can choose from here whether to debug an executable, a web application (either in IIS or from VS’s web development server), windows services, etc. So I chose a .NET Executable and navigated to the build location of my test harness.  Then began profiling. At this point while the application is running, you can see a chart of the memory as it ebbs and wanes with allocations and collections.  At any given point in time, you can take snapshots (to compare states) zoom in, or choose to stop at any time.  Snapshots Taking a snapshot also gives you a breakdown of the managed memory heaps for each generation so you get an idea how many objects are staying around for extended periods of time (as an object lives and survives collections, it gets promoted into higher generations where collection becomes less frequent). Generating a snapshot brings up an analysis view with very handy graphs that show your generation sizes.  Almost all my memory is in Generation 1 in the managed memory component of the first graph, which is good news to me, because Gen 2 collections are much rarer.  I once3 made the mistake once of caching data for 30 minutes and found it didn’t get collected very quick after I released my reference because it had been promoted to Gen 2 – doh! Analysis It looks like (from the second pie chart) that the majority of the allocations were in the string class.  This also is expected for me because the majority of the memory allocated is in the web service responses, so it doesn’t seem the entities I’m adapting to (to prevent being too tightly coupled to the web service proxy classes, which can change easily out from under me) aren’t taking a significant portion of memory. I also appreciate that they have clear summary text in key places such as “No issues with large object heap fragmentation were detected”.  For novice users, this type of summary information can be critical to getting them to use a tool and develop a good working knowledge of it. There is also a handy link at the bottom for “What to look for on the summary” which loads a web page of help on key points to look for. Clicking over to the session overview, it’s easy to compare the samples at each snapshot to see how your memory is growing, shrinking, or staying relatively the same.  Looking at my snapshots, I’m pretty happy with the fact that memory allocation and heap size seems to be fairly stable and in control: Once again, you can check on the large object heap, generation one heap, and generation two heap across each snapshot to spot trends. Back on the analysis tab, we can go to the [Class List] button to get an idea what classes are making up the majority of our memory usage.  As was little surprise to me, System.String was the clear majority of my allocations, though I found it surprising that the System.Reflection.RuntimeMehtodInfo came in second.  I was curious about this, so I selected it and went into the [Instance Categorizer].  This view let me see where these instances to RuntimeMehtodInfo were coming from. So I scrolled back through the graph, and discovered that these were being held by the System.ServiceModel.ChannelFactoryRefCache and I was satisfied this was just an artifact of my WCF proxy. I also like that down at the bottom of the Instance Categorizer it gives you a series of filters and offers to guide you on which filter to use based on the problem you are trying to find.  For example, if I suspected a memory leak, I might try to filter for survivors in growing classes.  This means that for instances of a class that are growing in memory (more are being created than cleaned up), which ones are survivors (not collected) from garbage collection.  This might allow me to drill down and find places where I’m holding onto references by mistake and not freeing them! Finally, if you want to really see all your instances and who is holding onto them (preventing collection), you can go to the “Instance Retention Graph” which creates a graph showing what references are being held in memory and who is holding onto them. Visual Studio Integration Of course, VS has its own profiler built in – and for a free bundled profiler it is quite capable – but AMP gives a much cleaner and easier-to-use experience, and when you install it you also get the option of letting it integrate directly into VS. So once you go back into VS after installation, you’ll notice an ANTS menu which lets you launch the ANTS profiler directly from Visual Studio.   Clicking on one of these options fires up the project in the profiler immediately, allowing you to get right in.  It doesn’t integrate with the Visual Studio windows themselves (like the VS profiler does), but still the plethora of information it provides and the clear and concise manner in which it presents it makes it well worth it. Summary If you like the ANTS series of tools, you shouldn’t be disappointed with the ANTS Memory Profiler.  It was so easy to use that I was able to jump in with very little product knowledge and get the information I was looking it for. I’ve used other profilers before that came with 3-inch thick tomes that you had to read in order to get anywhere with the tool, and this one is not like that at all.  It’s built for your everyday developer to get in and find their problems quickly, and I like that! Tweet Technorati Tags: Influencers,ANTS,Memory,Profiler

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• Adding and accessing custom sections in your C# App.config

  - by deadlydog

  So I recently thought I’d try using the app.config file to specify some data for my application (such as URLs) rather than hard-coding it into my app, which would require a recompile and redeploy of my app if one of our URLs changed.  By using the app.config it allows a user to just open up the .config file that sits beside their .exe file and edit the URLs right there and then re-run the app; no recompiling, no redeployment necessary. I spent a good few hours fighting with the app.config and looking at examples on Google before I was able to get things to work properly.  Most of the examples I found showed you how to pull a value from the app.config if you knew the specific key of the element you wanted to retrieve, but it took me a while to find a way to simply loop through all elements in a section, so I thought I would share my solutions here.   Simple and Easy The easiest way to use the app.config is to use the built-in types, such as NameValueSectionHandler.  For example, if we just wanted to add a list of database server urls to use in my app, we could do this in the app.config file like so: 1: <?xml version="1.0" encoding="utf-8" ?> 2: <configuration> 3: <configSections> 4: <section name="ConnectionManagerDatabaseServers" type="System.Configuration.NameValueSectionHandler" /> 5: </configSections> 6: <startup> 7: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" /> 8: </startup> 9: <ConnectionManagerDatabaseServers> 10: <add key="localhost" value="localhost" /> 11: <add key="Dev" value="Dev.MyDomain.local" /> 12: <add key="Test" value="Test.MyDomain.local" /> 13: <add key="Live" value="Prod.MyDomain.com" /> 14: </ConnectionManagerDatabaseServers> 15: </configuration>   And then you can access these values in code like so: 1: string devUrl = string.Empty; 2: var connectionManagerDatabaseServers = ConfigurationManager.GetSection("ConnectionManagerDatabaseServers") as NameValueCollection; 3: if (connectionManagerDatabaseServers != null) 4: { 5: devUrl = connectionManagerDatabaseServers["Dev"].ToString(); 6: }   Sometimes though you don’t know what the keys are going to be and you just want to grab all of the values in that ConnectionManagerDatabaseServers section.  In that case you can get them all like this: 1: // Grab the Environments listed in the App.config and add them to our list. 2: var connectionManagerDatabaseServers = ConfigurationManager.GetSection("ConnectionManagerDatabaseServers") as NameValueCollection; 3: if (connectionManagerDatabaseServers != null) 4: { 5: foreach (var serverKey in connectionManagerDatabaseServers.AllKeys) 6: { 7: string serverValue = connectionManagerDatabaseServers.GetValues(serverKey).FirstOrDefault(); 8: AddDatabaseServer(serverValue); 9: } 10: }   And here we just assume that the AddDatabaseServer() function adds the given string to some list of strings.  So this works great, but what about when we want to bring in more values than just a single string (or technically you could use this to bring in 2 strings, where the “key” could be the other string you want to store; for example, we could have stored the value of the Key as the user-friendly name of the url).   More Advanced (and more complicated) So if you want to bring in more information than a string or two per object in the section, then you can no longer simply use the built-in System.Configuration.NameValueSectionHandler type provided for us.  Instead you have to build your own types.  Here let’s assume that we again want to configure a set of addresses (i.e. urls), but we want to specify some extra info with them, such as the user-friendly name, if they require SSL or not, and a list of security groups that are allowed to save changes made to these endpoints. So let’s start by looking at the app.config: 1: <?xml version="1.0" encoding="utf-8" ?> 2: <configuration> 3: <configSections> 4: <section name="ConnectionManagerDataSection" type="ConnectionManagerUpdater.Data.Configuration.ConnectionManagerDataSection, ConnectionManagerUpdater" /> 5: </configSections> 6: <startup> 7: <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" /> 8: </startup> 9: <ConnectionManagerDataSection> 10: <ConnectionManagerEndpoints> 11: <add name="Development" address="Dev.MyDomain.local" useSSL="false" /> 12: <add name="Test" address="Test.MyDomain.local" useSSL="true" /> 13: <add name="Live" address="Prod.MyDomain.com" useSSL="true" securityGroupsAllowedToSaveChanges="ConnectionManagerUsers" /> 14: </ConnectionManagerEndpoints> 15: </ConnectionManagerDataSection> 16: </configuration>   The first thing to notice here is that my section is now using the type “ConnectionManagerUpdater.Data.Configuration.ConnectionManagerDataSection” (the fully qualified path to my new class I created) “, ConnectionManagerUpdater” (the name of the assembly my new class is in).  Next, you will also notice an extra layer down in the <ConnectionManagerDataSection> which is the <ConnectionManagerEndpoints> element.  This is a new collection class that I created to hold each of the Endpoint entries that are defined.  Let’s look at that code now: 1: using System; 2: using System.Collections.Generic; 3: using System.Configuration; 4: using System.Linq; 5: using System.Text; 6: using System.Threading.Tasks; 7:  8: namespace ConnectionManagerUpdater.Data.Configuration 9: { 10: public class ConnectionManagerDataSection : ConfigurationSection 11: { 12: /// <summary> 13: /// The name of this section in the app.config. 14: /// </summary> 15: public const string SectionName = "ConnectionManagerDataSection"; 16: 17: private const string EndpointCollectionName = "ConnectionManagerEndpoints"; 18:  19: [ConfigurationProperty(EndpointCollectionName)] 20: [ConfigurationCollection(typeof(ConnectionManagerEndpointsCollection), AddItemName = "add")] 21: public ConnectionManagerEndpointsCollection ConnectionManagerEndpoints { get { return (ConnectionManagerEndpointsCollection)base[EndpointCollectionName]; } } 22: } 23:  24: public class ConnectionManagerEndpointsCollection : ConfigurationElementCollection 25: { 26: protected override ConfigurationElement CreateNewElement() 27: { 28: return new ConnectionManagerEndpointElement(); 29: } 30: 31: protected override object GetElementKey(ConfigurationElement element) 32: { 33: return ((ConnectionManagerEndpointElement)element).Name; 34: } 35: } 36: 37: public class ConnectionManagerEndpointElement : ConfigurationElement 38: { 39: [ConfigurationProperty("name", IsRequired = true)] 40: public string Name 41: { 42: get { return (string)this["name"]; } 43: set { this["name"] = value; } 44: } 45: 46: [ConfigurationProperty("address", IsRequired = true)] 47: public string Address 48: { 49: get { return (string)this["address"]; } 50: set { this["address"] = value; } 51: } 52: 53: [ConfigurationProperty("useSSL", IsRequired = false, DefaultValue = false)] 54: public bool UseSSL 55: { 56: get { return (bool)this["useSSL"]; } 57: set { this["useSSL"] = value; } 58: } 59: 60: [ConfigurationProperty("securityGroupsAllowedToSaveChanges", IsRequired = false)] 61: public string SecurityGroupsAllowedToSaveChanges 62: { 63: get { return (string)this["securityGroupsAllowedToSaveChanges"]; } 64: set { this["securityGroupsAllowedToSaveChanges"] = value; } 65: } 66: } 67: }   So here the first class we declare is the one that appears in the <configSections> element of the app.config.  It is ConnectionManagerDataSection and it inherits from the necessary System.Configuration.ConfigurationSection class.  This class just has one property (other than the expected section name), that basically just says I have a Collection property, which is actually a ConnectionManagerEndpointsCollection, which is the next class defined.  The ConnectionManagerEndpointsCollection class inherits from ConfigurationElementCollection and overrides the requied fields.  The first tells it what type of Element to create when adding a new one (in our case a ConnectionManagerEndpointElement), and a function specifying what property on our ConnectionManagerEndpointElement class is the unique key, which I’ve specified to be the Name field. The last class defined is the actual meat of our elements.  It inherits from ConfigurationElement and specifies the properties of the element (which can then be set in the xml of the App.config).  The “ConfigurationProperty” attribute on each of the properties tells what we expect the name of the property to correspond to in each element in the app.config, as well as some additional information such as if that property is required and what it’s default value should be. Finally, the code to actually access these values would look like this: 1: // Grab the Environments listed in the App.config and add them to our list. 2: var connectionManagerDataSection = ConfigurationManager.GetSection(ConnectionManagerDataSection.SectionName) as ConnectionManagerDataSection; 3: if (connectionManagerDataSection != null) 4: { 5: foreach (ConnectionManagerEndpointElement endpointElement in connectionManagerDataSection.ConnectionManagerEndpoints) 6: { 7: var endpoint = new ConnectionManagerEndpoint() { Name = endpointElement.Name, ServerInfo = new ConnectionManagerServerInfo() { Address = endpointElement.Address, UseSSL = endpointElement.UseSSL, SecurityGroupsAllowedToSaveChanges = endpointElement.SecurityGroupsAllowedToSaveChanges.Split(',').Where(e => !string.IsNullOrWhiteSpace(e)).ToList() } }; 8: AddEndpoint(endpoint); 9: } 10: } This looks very similar to what we had before in the “simple” example.  The main points of interest are that we cast the section as ConnectionManagerDataSection (which is the class we defined for our section) and then iterate over the endpoints collection using the ConnectionManagerEndpoints property we created in the ConnectionManagerDataSection class.   Also, some other helpful resources around using app.config that I found (and for parts that I didn’t really explain in this article) are: How do you use sections in C# 4.0 app.config? (Stack Overflow) <== Shows how to use Section Groups as well, which is something that I did not cover here, but might be of interest to you. How to: Create Custom Configuration Sections Using Configuration Section (MSDN) ConfigurationSection Class (MSDN) ConfigurationCollectionAttribute Class (MSDN) ConfigurationElementCollection Class (MSDN)   I hope you find this helpful.  Feel free to leave a comment.  Happy Coding!

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