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  • Exception Handling Differences Between 32/64 Bit

    - by Alois Kraus
    I do quite a bit of debugging .NET applications but from time to time I see things that are impossible (at a first look). I may ask you dear reader what your mental exception handling model is. Exception handling is easy after all right? Lets suppose the following code:         private void F1(object sender, EventArgs e)         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new Exception("even worse Exception");             }           }           private void F2()         {             try             {                 F3();             }             finally             {                 throw new Exception("other exception");             }         }           private void F3()         {             throw new NotImplementedException();         }   What will the call stack look like when you break into the catch(Exception) clause in Windbg (32 and 64 bit on .NET 3.5 SP1)? The mental model I have is that when an exception is thrown the stack frames are unwound until the catch handler can execute. An exception does propagate the call chain upwards.   So when F3 does throw an exception the control flow will resume at the finally handler in F2 which does throw another exception hiding the original one (that is nasty) and then the new Exception will be catched in F1 where the catch handler is executed. So we should see in the catch handler in F1 as call stack only the F1 stack frame right? Well lets try it out in Windbg. For this I created a simple Windows Forms application with one button which does execute the F1 method in its click handler. When you compile the application for 64 bit and the catch handler is reached you will find with the following commands in Windbg   Load sos extension from the same path where mscorwks was loaded in the current process .loadby sos mscorwks   Beak on clr exceptions sxe clr   Continue execution g   Dump mixed call stack container C++  and .NET Stacks interleaved 0:000> !DumpStack OS Thread Id: 0x1d8 (0) Child-SP         RetAddr          Call Site 00000000002c88c0 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002c8990 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002c8a60 000007ff005dd7f4 mscorwks!JIT_Throw+0x130 00000000002c8c10 000007fefa6942e1 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)+0xb4 00000000002c8c60 000007fefa661012 mscorwks!ExceptionTracker::CallHandler+0x145 00000000002c8d60 000007fefa711a72 mscorwks!ExceptionTracker::CallCatchHandler+0x9e 00000000002c8df0 0000000077b055cd mscorwks!ProcessCLRException+0x25e 00000000002c8e90 0000000077ae55f8 ntdll!RtlpExecuteHandlerForUnwind+0xd 00000000002c8ec0 000007fefa637c1a ntdll!RtlUnwindEx+0x539 00000000002c9560 000007fefa711a21 mscorwks!ClrUnwindEx+0x36 00000000002c9a70 0000000077b0554d mscorwks!ProcessCLRException+0x20d 00000000002c9b10 0000000077ae5d1c ntdll!RtlpExecuteHandlerForException+0xd 00000000002c9b40 0000000077b1fe48 ntdll!RtlDispatchException+0x3cb 00000000002ca220 000007fefdaeaa7d ntdll!KiUserExceptionDispatcher+0x2e 00000000002ca7e0 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002ca8b0 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002ca980 000007ff005dd8df mscorwks!JIT_Throw+0x130 00000000002cab30 000007fefa6942e1 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F2()+0x9f 00000000002cab80 000007fefa71b5b3 mscorwks!ExceptionTracker::CallHandler+0x145 00000000002cac80 000007fefa70dcd0 mscorwks!ExceptionTracker::ProcessManagedCallFrame+0x683 00000000002caed0 000007fefa7119af mscorwks!ExceptionTracker::ProcessOSExceptionNotification+0x430 00000000002cbd90 0000000077b055cd mscorwks!ProcessCLRException+0x19b 00000000002cbe30 0000000077ae55f8 ntdll!RtlpExecuteHandlerForUnwind+0xd 00000000002cbe60 000007fefa637c1a ntdll!RtlUnwindEx+0x539 00000000002cc500 000007fefa711a21 mscorwks!ClrUnwindEx+0x36 00000000002cca10 0000000077b0554d mscorwks!ProcessCLRException+0x20d 00000000002ccab0 0000000077ae5d1c ntdll!RtlpExecuteHandlerForException+0xd 00000000002ccae0 0000000077b1fe48 ntdll!RtlDispatchException+0x3cb 00000000002cd1c0 000007fefdaeaa7d ntdll!KiUserExceptionDispatcher+0x2e 00000000002cd780 000007fefa68f0bd KERNELBASE!RaiseException+0x39 00000000002cd850 000007fefac42ed0 mscorwks!RaiseTheExceptionInternalOnly+0x295 00000000002cd920 000007ff005dd968 mscorwks!JIT_Throw+0x130 00000000002cdad0 000007ff005dd875 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F3()+0x48 00000000002cdb10 000007ff005dd786 WindowsFormsApplication1!WindowsFormsApplication1.Form1.F2()+0x35 00000000002cdb60 000007ff005dbe6a WindowsFormsApplication1!WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)+0x46 00000000002cdbc0 000007ff005dd452 System_Windows_Forms!System.Windows.Forms.Control.OnClick(System.EventArgs)+0x5a   Hm okaaay. I see my method F1 two times in this call stack. Looks like we did get some recursion bug. But that can´t be given the obvious code above. Let´s try the same thing in a 32 bit process.  0:000> !DumpStack OS Thread Id: 0x33e4 (0) Current frame: KERNELBASE!RaiseException+0x58 ChildEBP RetAddr  Caller,Callee 0028ed38 767db727 KERNELBASE!RaiseException+0x58, calling ntdll!RtlRaiseException 0028ed4c 68b9008c mscorwks!Binder::RawGetClass+0x20, calling mscorwks!Module::LookupTypeDef 0028ed5c 68b904ff mscorwks!Binder::IsClass+0x23, calling mscorwks!Binder::RawGetClass 0028ed68 68bfb96f mscorwks!Binder::IsException+0x14, calling mscorwks!Binder::IsClass 0028ed78 68bfb996 mscorwks!IsExceptionOfType+0x23, calling mscorwks!Binder::IsException 0028ed80 68bfbb1c mscorwks!RaiseTheExceptionInternalOnly+0x2a8, calling KERNEL32!RaiseExceptionStub 0028eda8 68ba0713 mscorwks!Module::ResolveStringRef+0xe0, calling mscorwks!BaseDomain::GetStringObjRefPtrFromUnicodeString 0028edc8 68b91e8d mscorwks!SetObjectReferenceUnchecked+0x19 0028ede0 68c8e910 mscorwks!JIT_Throw+0xfc, calling mscorwks!RaiseTheExceptionInternalOnly 0028ee44 68c8e734 mscorwks!JIT_StrCns+0x22, calling mscorwks!LazyMachStateCaptureState 0028ee54 68c8e865 mscorwks!JIT_Throw+0x1e, calling mscorwks!LazyMachStateCaptureState 0028eea4 02ffaecd (MethodDesc 0x7af08c +0x7d WindowsFormsApplication1.Form1.F1(System.Object, System.EventArgs)), calling mscorwks!JIT_Throw 0028eeec 02ffaf19 (MethodDesc 0x7af098 +0x29 WindowsFormsApplication1.Form1.F2()), calling 06370634 0028ef58 02ffae37 (MethodDesc 0x7a7bb0 +0x4f System.Windows.Forms.Control.OnClick(System.EventArgs))   That does look more familar. The call stack has been unwound and we do see only some frames into the history where the debugger was smart enough to find out that we have called F2 from F1. The exception handling on 64 bit systems does work quite differently which seems to have the nice property to remember the called methods not only during the first pass of exception filter clauses (during first pass all catch handler are called if they are going to catch the exception which is about to be thrown)  but also when the actual stack unwind has taken place. This makes it possible to follow not only the call stack right at the moment but also to look into the “history” of the catch/finally clauses. In a 64 bit process you only need to look at the ExceptionTracker to find out if a catch or finally handler was called. The two frames ProcessManagedCallFrame/CallHandler does indicate a finally clause whereas CallCatchHandler/CallHandler indicates a catch clause. That was a interesting one. Oh and by the way if you manage to load the Microsoft symbols you can also find out the hidden exception which. When you encounter in the call stack a line 0016eb34 75b79617 KERNELBASE!RaiseException+0x58 ====> Exception Code e0434f4d cxr@16e850 exr@16e838 Then it is a good idea to execute .exr 16e838 !analyze –v to find out more. In the managed world it is even easier since we can dump the objects allocated on the stack which have not yet been garbage collected to look at former method parameters. The command !dso which is the abbreviation for dump stack objects will give you 0:000> !dso OS Thread Id: 0x46c (0) ESP/REG  Object   Name 0016dd4c 020737f0 System.Exception 0016dd98 020737f0 System.Exception 0016dda8 01f5c6cc System.Windows.Forms.Button 0016ddac 01f5d2b8 System.EventHandler 0016ddb0 02071744 System.Windows.Forms.MouseEventArgs 0016ddc0 01f5d2b8 System.EventHandler 0016ddcc 01f5c6cc System.Windows.Forms.Button 0016dddc 020737f0 System.Exception 0016dde4 01f5d2b8 System.EventHandler 0016ddec 02071744 System.Windows.Forms.MouseEventArgs 0016de40 020737f0 System.Exception 0016de80 02071744 System.Windows.Forms.MouseEventArgs 0016de8c 01f5d2b8 System.EventHandler 0016de90 01f5c6cc System.Windows.Forms.Button 0016df10 02073784 System.SByte[] 0016df5c 02073684 System.NotImplementedException 0016e2a0 02073684 System.NotImplementedException 0016e2e8 01ed69f4 System.Resources.ResourceManager From there it is easy to do 0:000> !pe 02073684 Exception object: 02073684 Exception type: System.NotImplementedException Message: Die Methode oder der Vorgang sind nicht implementiert. InnerException: <none> StackTrace (generated):     SP       IP       Function     0016ECB0 006904AD WindowsFormsApplication2!WindowsFormsApplication2.Form1.F3()+0x35     0016ECC0 00690411 WindowsFormsApplication2!WindowsFormsApplication2.Form1.F2()+0x29     0016ECF0 0069038F WindowsFormsApplication2!WindowsFormsApplication2.Form1.F1(System.Object, System.EventArgs)+0x3f StackTraceString: <none> HResult: 80004001 to see the former exception. That´s all for today.

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  • It's intellisense for SQL Server

    - by Nick Harrison
    It's intellisense for SQL Server Anyone who has ever worked with me, heard me speak, or read any of writings knows that I am a HUGE fan of Reflector.    By extension,  I am a big fan of Red - Gate   I have recently begun exploring some of their other offerings and came across this jewel. SQL Prompt is a plug in for Visual Studio and SQL Server Management Studio.    It provides several tools to make dealing with SQL a little easier for your friendly neighborhood developer. When you a query window in a database, the plugin kicks in and gathers the metadata for the database that you are in.    As you type a query, you get handy feedback like a list of tables after you type select.    You can select one of the tables, specify * and then tab to expand the select clause to include all of the columns from the selected table.    As you are building up the where clause, you are prompted by the names of columns in the selected tables. If you spend any time writing ad hoc queries or building stored procedures by hand, this can save you substantial time. If you are learning a new data model, this can greatly cut down on your frustration level. The other really cool thing here is Format SQL.   I have searched all over the place for a really good SQL formatter.    Badly formatted  SQL is so much harder to read than well formatted SQL.   Unfortunately, management studio offers no support for keeping your SQL well formatted.    There are many tools available to format your SQL.   Some work better than others.    Some don't work that well at all.   Most will give you some measure of control over how the formatted SQL looks.    SQL Prompt produces good results and is easy to configure. Sadly no tool is perfect, and what would we be without a wish list.    There are some features that I would like to see: Make it easier to paste SQL in and out of code.    Strip off string builder, etc Automate replacing hard coded values with bind variables or parameters In addition to reformatting SQL, which is a huge refactor, support for other SQL refactors would be nice.    Convert join to sub query and vice versa come to mind Wish list a side, this is a wonderful tool that easily saves me an hour or more on most weeks.

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  • SQL Server Select

    - by Derek D.
    The SQL Server Select statement is the first statement used when returning data. It is the most used and most important statement in the T-SQL language. The Select statement has many different clauses. We will step through each clause further in the tutorial, however now, we will look at Select itself. The following [...]

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  • C# Role Provider for multiple applications

    - by Juventus18
    I'm making a custom RoleProvider that I would like to use across multiple applications in the same application pool. For the administration of roles (create new role, add users to role, etc..) I would like to create a master application that I could login to and set the roles for each additional application. So for example, I might have AppA and AppB in my organization, and I need to make an application called AppRoleManager that can set roles for AppA and AppB. I am having troubles implementing my custom RoleProvider because it uses an initialize method that gets the application name from the config file, but I need the application name to be a variable (i.e. "AppA" or "AppB") and passed as a parameter. I thought about just implementing the required methods, and then also having additional methods that pass application name as a parameter, but that seems clunky. i.e. public override CreateRole(string roleName) { //uses the ApplicationName property of this, which is set in web.config //creates role in db } public CreateRole(string ApplicationName, string roleName) { //creates role in db with specified params. } Also, I would prefer if people were prevented from calling CreateRole(string roleName) because the current instance of the class might have a different applicationName value than intended (what should i do here? throw NotImplementedException?). I tried just writing the class without inheriting RoleProvider. But it is required by the framework. Any general ideas on how to structure this project? I was thinking make a wrapper class that uses the role provider, and explicitly sets the application name before (and after) and calls to the provider something like this: static class RoleProviderWrapper { public static CreateRole(string pApplicationName, string pRoleName) { Roles.Provider.ApplicationName = pApplicationName; Roles.Provider.CreateRole(pRoleName); Roles.Provider.ApplicationName = "Generic"; } } is this my best-bet?

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  • SQL Server 2008 R2: StreamInsight changes at RTM: Access to grouping keys via explicit typing

    - by Greg Low
    One of the problems that existed in the CTP3 edition of StreamInsight was an error that occurred if you tried to access the grouping key from within your projection expression. That was a real issue as you always need access to the key. It's a bit like using a GROUP BY in TSQL and then not including the columns you're grouping by in the SELECT clause. You'd see the results but not be able to know which results are which. Look at the following code: var laneSpeeds = from e in vehicleSpeeds group e...(read more)

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  • Geek City: Where are LOBs stored?

    - by Kalen Delaney
    When researching a question from one of the students in my class last week, I was reading the documentation for CREATE TABLE about storing LOB columns at http://msdn.microsoft.com/en-us/library/ms174979.aspx . For this discussion LOB columns includes text, image, ntext, xml and the MAX columns when they are over 8000 bytes and stored outside the regular data row. I knew that SQL Server gives us the capability of storing LOB columns in a separate filegroup with the TEXTIMAGE_ON clause, but I was surprised...(read more)

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  • Is LINQ to objects a collection of combinators?

    - by Jimmy Hoffa
    I was just trying to explain the usefulness of combinators to a colleague and I told him LINQ to objects are like combinators as they exhibit the same value, the ability to combine small pieces to create a single large piece. Though I don't know that I can call LINQ to objects combinators. I've seen 2 levels of definition for combinator that I generalize as such: A combinator is a function which only uses things passed to it A combinator is a function which only uses things passed to it and other standard atomic functions but not state The first is very rigid and can be seen in the combinatory calculus systems and in haskell things like $ and . and various similar functions meet this rule. The second is less rigid and would allow something like sum as it uses the + function which was not passed in but is standard and not stateful. Though the LINQ extensions in C# use state in their iteration models, so I feel I can't say they're combinators. Can someone who understands the definition of a combinator more thoroughly and with more experience in these realms give a distinct ruling on this? Are my definitions of 'combinator' wrong to begin with?

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  • Find Duplicate Items in a Table

    - by Derek Dieter
    A very common scenario when querying tables is the need to find duplicate items within the same table. To do this is simple, it requires utilizing the GROUP BY clause and counting the number of recurrences. For example, lets take a customers table. Within the customers table, we want to find all [...]

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  • I'm confused about encryption and SSL

    - by ChowKiko
    while my friends and I planning to run our own website, we're confused about the encryption where hackers can TAPPING or in social engineering it's WIRE TAPPING, but I don't know how do they call it in Computers today... Well guys, I just want to know how encryption works with websites if we are using PHP+MYSQL? Is it ok to use user login ---- (PHP) encrypt inputted value then (PHP) will decrypt and validate it going to (MySQL) user login ---- (PHP) encrypt inputted value and decrypt the (MySQL) data if they are similar... Is it similar if we use $_SESSION without encryption inside PHP going to MySQL?or PHP encryption also helps the manipulation of binaries?..I'm so confused T_T... In regards to what I stated above, can a hacker hook the data if the server uses $_SESSION? Is $_SESSION safe?... IF THE HACKER CAN HOOK it? is it necessary to use SSL on our website? and why do some Merchandise websites use SSL and likewise facebook also uses SSL? what is the best suit for you if there is no SSL? encrypting the DATA using PHP going to MySQL or even without encryption while the PHP server uses $_SESSION?...

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  • SQL Server Table Polling by Multiple Subscribers

    - by Daniel Hester
    Background Designing Stored Procedures that are safe for multiple subscribers (to call simultaneously) can be challenging.  For example let’s say that you want multiple worker processes to poll a shared work queue that’s encapsulated as a SQL Table. This is a common scenario and through experience you’ll find that you want to use Table Hints to prevent unwanted locking when performing simultaneous queries on the same table. There are three table hints to consider: NOLOCK, READPAST and UPDLOCK. Both NOLOCK and READPAST table hints allow you to SELECT from a table without placing a LOCK on that table. However, SELECTs with the READPAST hint will ignore any records that are locked due to being updated/inserted (or otherwise “dirty”), whereas a SELECT with NOLOCK ignores all locks including dirty reads. For the initial update of the flag (that marks the record as available for subscription) I don’t use the NOLOCK Table Hint because I want to be sensitive to the “active” records in the table and I want to exclude them.  I use an Update Lock (UPDLOCK) in conjunction with a WHERE clause that uses a sub-select with a READPAST Table Hint in order to explicitly lock the records I’m updating (UPDLOCK) but not place a lock on the table when selecting the records that I’m going to update (READPAST). UPDATES should be allowed to lock the rows affected because we’re probably changing a flag on a record so that it is not included in a SELECT from another subscriber. On the UPDATE statement we should explicitly use the UPDLOCK to guard against lock escalation. A SELECT to check for the next record(s) to process can result in a shared read lock being held by more than one subscriber polling the shared work queue (SQL table). It is expected that more than one worker process (or server) might try to process the same new record(s) at the same time. When each process then tries to obtain the update lock, none of them can because another process has a shared read lock in place. Thus without the UPDLOCK hint the result would be a lock escalation deadlock; however with the UPDLOCK hint this condition is mitigated against. Note that using the READPAST table hint requires that you also set the ISOLATION LEVEL of the transaction to be READ COMMITTED (rather than the default of SERIALIZABLE). Guidance In the Stored Procedure that returns records to the multiple subscribers: Perform the UPDATE first. Change the flag that makes the record available to subscribers.  Additionally, you may want to update a LastUpdated datetime field in order to be able to check for records that “got stuck” in an intermediate state or for other auditing purposes. In the UPDATE statement use the (UPDLOCK) Table Hint on the UPDATE statement to prevent lock escalation. In the UPDATE statement also use a WHERE Clause that uses a sub-select with a (READPAST) Table Hint to select the records that you’re going to update. In the UPDATE statement use the OUTPUT clause in conjunction with a Temporary Table to isolate the record(s) that you’ve just updated and intend to return to the subscriber. This is the fastest way to update the record(s) and to get the records’ identifiers within the same operation. Finally do a set-based SELECT on the main Table (using the Temporary Table to identify the records in the set) with either a READPAST or NOLOCK table hint.  Use NOLOCK if there are other processes (besides the multiple subscribers) that might be changing the data that you want to return to the multiple subscribers; or use READPAST if you're sure there are no other processes (besides the multiple subscribers) that might be updating column data in the table for other purposes (e.g. changes to a person’s last name).  NOLOCK is generally the better fit in this part of the scenario. See the following as an example: CREATE PROCEDURE [dbo].[usp_NewCustomersSelect] AS BEGIN -- OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON -- DECLARE TEMP TABLE -- Note that this example uses CustomerId as an identifier; -- you could just use the Identity column Id if that’s all you need. DECLARE @CustomersTempTable TABLE ( CustomerId NVARCHAR(255) ) -- PERFORM UPDATE FIRST -- [Customers] is the name of the table -- [Id] is the Identity Column on the table -- [CustomerId] is the business document key used to identify the -- record globally, i.e. in other systems or across SQL tables -- [Status] is INT or BIT field (if the status is a binary state) -- [LastUpdated] is a datetime field used to record the time of the -- last update UPDATE [Customers] WITH (UPDLOCK) SET [Status] = 1, [LastUpdated] = GETDATE() OUTPUT [INSERTED].[CustomerId] INTO @CustomersTempTable WHERE ([Id] = (SELECT TOP 100 [Id] FROM [Customers] WITH (READPAST) WHERE ([Status] = 0) ORDER BY [Id] ASC)) -- PERFORM SELECT FROM ENTITY TABLE SELECT [C].[CustomerId], [C].[FirstName], [C].[LastName], [C].[Address1], [C].[Address2], [C].[City], [C].[State], [C].[Zip], [C].[ShippingMethod], [C].[Id] FROM [Customers] AS [C] WITH (NOLOCK), @CustomersTempTable AS [TEMP] WHERE ([C].[CustomerId] = [TEMP].[CustomerId]) END In a system that has been designed to have multiple status values for records that need to be processed in the Work Queue it is necessary to have a “Watch Dog” process by which “stale” records in intermediate states (such as “In Progress”) are detected, i.e. a [Status] of 0 = New or Unprocessed; a [Status] of 1 = In Progress; a [Status] of 2 = Processed; etc.. Thus, if you have a business rule that states that the application should only process new records if all of the old records have been processed successfully (or marked as an error), then it will be necessary to build a monitoring process to detect stalled or stale records in the Work Queue, hence the use of the LastUpdated column in the example above. The Status field along with the LastUpdated field can be used as the criteria to detect stalled / stale records. It is possible to put this watchdog logic into the stored procedure above, but I would recommend making it a separate monitoring function. In writing the stored procedure that checks for stale records I would recommend using the same kind of lock semantics as suggested above. The example below looks for records that have been in the “In Progress” state ([Status] = 1) for greater than 60 seconds: CREATE PROCEDURE [dbo].[usp_NewCustomersWatchDog] AS BEGIN -- TO OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON DECLARE @MaxWait int; SET @MaxWait = 60 IF EXISTS (SELECT 1 FROM [dbo].[Customers] WITH (READPAST) WHERE ([Status] = 1) AND (DATEDIFF(s, [LastUpdated], GETDATE()) > @MaxWait)) BEGIN SELECT 1 AS [IsWatchDogError] END ELSE BEGIN SELECT 0 AS [IsWatchDogError] END END Downloads The zip file below contains two SQL scripts: one to create a sample database with the above stored procedures and one to populate the sample database with 10,000 sample records.  I am very grateful to Red-Gate software for their excellent SQL Data Generator tool which enabled me to create these sample records in no time at all. References http://msdn.microsoft.com/en-us/library/ms187373.aspx http://www.techrepublic.com/article/using-nolock-and-readpast-table-hints-in-sql-server/6185492 http://geekswithblogs.net/gwiele/archive/2004/11/25/15974.aspx http://grounding.co.za/blogs/romiko/archive/2009/03/09/biztalk-sql-receive-location-deadlocks-dirty-reads-and-isolation-levels.aspx

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  • Can I use all my RAM for application data?

    - by gsedej
    Hi! I have yet another question about "where is my Linux memory" Question goes: can I use cache for application data? On my laptop I have 1GB ram. Situation after some time of work: browser takes 400MB and all other apps caa 300MB (quickly summed in system monitor). System monitor says I use 90% of RAM and I have already 200MB on swap. Laptop is getting slower when I start new things (e.g. open new tab in browser or open new Nautilus window). probably putting memory on swap So there should be 1200MB (ram+swap) used but all app I see uses only 600MB. Where are other 600MB? Out of this 600MB there is 400MB real RAM. I am not copying or any other massive IO activity. I read about Linux smartly uses all ram it has using buffers and cache. So, kernel (cache) uses 300MB. What if I don't want to have disk mirrored and I want to use memory for application data (e.g. new browser tab)? I don't need 200MB of mirrored disk data, because I (for example) won't use open the same photos on data partition I just seen. So can I use all my RAM for application data? (including browser, desktop, xorg, other services). How?

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  • SQL Server Cast

    - by Derek Dieter
    The SQL Server cast function is the easiest data type conversion function to be used compared to the CONVERT function. It takes only one parameter followed by the AS clause to convert a specified value. A quick example is the following:SELECT UserID_String = CAST(UserID AS varchar(50)) FROM dbo.UserThis example will convert the integer to a character value. [...]

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  • Reasoner Conversion Problems:

    - by Annalyne
    I have this code right here in Java and I wanted to translate it in C++, but I had some problems going: this is the java code: import java.io.*; import java.util.*; public class ClueReasoner { private int numPlayers; private int playerNum; private int numCards; private SATSolver solver; private String caseFile = "cf"; private String[] players = {"sc", "mu", "wh", "gr", "pe", "pl"}; private String[] suspects = {"mu", "pl", "gr", "pe", "sc", "wh"}; private String[] weapons = {"kn", "ca", "re", "ro", "pi", "wr"}; private String[] rooms = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; private String[] cards; public ClueReasoner() { numPlayers = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; numCards = i; // Initialize solver solver = new SATSolver(); addInitialClauses(); } private int getPlayerNum(String player) { if (player.equals(caseFile)) return numPlayers; for (int i = 0; i < numPlayers; i++) if (player.equals(players[i])) return i; System.out.println("Illegal player: " + player); return -1; } private int getCardNum(String card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; System.out.println("Illegal card: " + card); return -1; } private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); } private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; } public void addInitialClauses() { // TO BE IMPLEMENTED AS AN EXERCISE // Each card is in at least one place (including case file). for (int c = 0; c < numCards; c++) { int[] clause = new int[numPlayers + 1]; for (int p = 0; p <= numPlayers; p++) clause[p] = getPairNum(p, c); solver.addClause(clause); } // If a card is one place, it cannot be in another place. // At least one card of each category is in the case file. // No two cards in each category can both be in the case file. } public void hand(String player, String[] cards) { playerNum = getPlayerNum(player); // TO BE IMPLEMENTED AS AN EXERCISE } public void suggest(String suggester, String card1, String card2, String card3, String refuter, String cardShown) { // TO BE IMPLEMENTED AS AN EXERCISE } public void accuse(String accuser, String card1, String card2, String card3, boolean isCorrect) { // TO BE IMPLEMENTED AS AN EXERCISE } public int query(String player, String card) { return solver.testLiteral(getPairNum(player, card)); } public String queryString(int returnCode) { if (returnCode == SATSolver.TRUE) return "Y"; else if (returnCode == SATSolver.FALSE) return "n"; else return "-"; } public void printNotepad() { PrintStream out = System.out; for (String player : players) out.print("\t" + player); out.println("\t" + caseFile); for (String card : cards) { out.print(card + "\t"); for (String player : players) out.print(queryString(query(player, card)) + "\t"); out.println(queryString(query(caseFile, card))); } } public static void main(String[] args) { ClueReasoner cr = new ClueReasoner(); String[] myCards = {"wh", "li", "st"}; cr.hand("sc", myCards); cr.suggest("sc", "sc", "ro", "lo", "mu", "sc"); cr.suggest("mu", "pe", "pi", "di", "pe", null); cr.suggest("wh", "mu", "re", "ba", "pe", null); cr.suggest("gr", "wh", "kn", "ba", "pl", null); cr.suggest("pe", "gr", "ca", "di", "wh", null); cr.suggest("pl", "wh", "wr", "st", "sc", "wh"); cr.suggest("sc", "pl", "ro", "co", "mu", "pl"); cr.suggest("mu", "pe", "ro", "ba", "wh", null); cr.suggest("wh", "mu", "ca", "st", "gr", null); cr.suggest("gr", "pe", "kn", "di", "pe", null); cr.suggest("pe", "mu", "pi", "di", "pl", null); cr.suggest("pl", "gr", "kn", "co", "wh", null); cr.suggest("sc", "pe", "kn", "lo", "mu", "lo"); cr.suggest("mu", "pe", "kn", "di", "wh", null); cr.suggest("wh", "pe", "wr", "ha", "gr", null); cr.suggest("gr", "wh", "pi", "co", "pl", null); cr.suggest("pe", "sc", "pi", "ha", "mu", null); cr.suggest("pl", "pe", "pi", "ba", null, null); cr.suggest("sc", "wh", "pi", "ha", "pe", "ha"); cr.suggest("wh", "pe", "pi", "ha", "pe", null); cr.suggest("pe", "pe", "pi", "ha", null, null); cr.suggest("sc", "gr", "pi", "st", "wh", "gr"); cr.suggest("mu", "pe", "pi", "ba", "pl", null); cr.suggest("wh", "pe", "pi", "st", "sc", "st"); cr.suggest("gr", "wh", "pi", "st", "sc", "wh"); cr.suggest("pe", "wh", "pi", "st", "sc", "wh"); cr.suggest("pl", "pe", "pi", "ki", "gr", null); cr.printNotepad(); cr.accuse("sc", "pe", "pi", "bi", true); } } how can I convert this? there are too many errors I get. for my C++ code (as a commentor asked for) #include <iostream> #include <cstdlib> #include <string> using namespace std; void Scene_Reasoner() { int numPlayer; int playerNum; int cardNum; string filecase = "Case: "; string players [] = {"sc", "mu", "wh", "gr", "pe", "pl"}; string suspects [] = {"mu", "pl", "gr", "pe", "sc", "wh"}; string weapons [] = {"kn", "ca", "re", "ro", "pi", "wr"}; string rooms[] = {"ha", "lo", "di", "ki", "ba", "co", "bi", "li", "st"}; string cards [0]; }; void Scene_Reason_Base () { numPlayer = players.length; // Initialize card info cards = new String[suspects.length + weapons.length + rooms.length]; int i = 0; for (String card : suspects) cards[i++] = card; for (String card : weapons) cards[i++] = card; for (String card : rooms) cards[i++] = card; cardNum = i; }; private int getCardNum (string card) { for (int i = 0; i < numCards; i++) if (card.equals(cards[i])) return i; cout << "Illegal card: " + card <<endl; return -1; }; private int getPairNum(String player, String card) { return getPairNum(getPlayerNum(player), getCardNum(card)); }; private int getPairNum(int playerNum, int cardNum) { return playerNum * numCards + cardNum + 1; }; int main () { return 0; }

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  • Positioning a sprite in XNA: Use ClientBounds or BackBuffer?

    - by Martin Andersson
    I'm reading a book called "Learning XNA 4.0" written by Aaron Reed. Throughout most of the chapters, whenever he calculates the position of a sprite to use in his call to SpriteBatch.Draw, he uses Window.ClientBounds.Width and Window.ClientBounds.Height. But then all of a sudden, on page 108, he uses PresentationParameters.BackBufferWidth and PresentationParameters.BackBufferHeight instead. I think I understand what the Back Buffer and the Client Bounds are and the difference between those two (or perhaps not?). But I'm mighty confused about when I should use one or the other when it comes to positioning sprites. The author uses for the most part Client Bounds both for checking whenever a moving sprite is of the screen and to find a spawn point for new sprites. However, he seems to make two exceptions from this pattern in his book. The first time is when he wants some animated sprites to "move in" and cross the screen from one side to another (page 108 as mentioned). The second and last time is when he positions a texture to work as a button in the lower right corner of a Windows Phone 7 screen (page 379). Anyone got an idea? I shall provide some context if it is of any help. Here's how he usually calls SpriteBatch.Draw (code example from where he positions a sprite in the middle of the screen [page 35]): spriteBatch.Draw(texture, new Vector2( (Window.ClientBounds.Width / 2) - (texture.Width / 2), (Window.ClientBounds.Height / 2) - (texture.Height / 2)), null, Color.White, 0, Vector2.Zero, 1, SpriteEffects.None, 0); And here is the first case of four possible in a switch statement that will set the position of soon to be spawned moving sprites, this position will later be used in the SpriteBatch.Draw call (page 108): // Randomly choose which side of the screen to place enemy, // then randomly create a position along that side of the screen // and randomly choose a speed for the enemy switch (((Game1)Game).rnd.Next(4)) { case 0: // LEFT to RIGHT position = new Vector2( -frameSize.X, ((Game1)Game).rnd.Next(0, Game.GraphicsDevice.PresentationParameters.BackBufferHeight - frameSize.Y)); speed = new Vector2(((Game1)Game).rnd.Next( enemyMinSpeed, enemyMaxSpeed), 0); break;

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  • Find Duplicate Fields in a Table

    - by Derek Dieter
    A common scenario when querying tables is the need to find duplicate fields within the same table. To do this is simple, it requires utilizing the GROUP BY clause and counting the number of recurrences. For example, lets take a customers table. Within the customers table, we want to find all the [...]

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  • 802.11 Capture Frame

    - by ALi
    I am using wireshark in monitor mode to capture all the frame. I buffered all the QosData in order to calculate the biterate of each station on the network. I calculate the biterate but it is not an accurate value. what i need to know is when the station use the network alone and when it uses it with another station? i know if two station with different wifi card for exemple ( st1 802.11g 54 Mb/s, st2 802.11n 300 Mb/s) if st1 uses alone the line the biterate used is 28 MB/s and if st2 uses alone the network the bit rate increase to approximately 150Mb/s but if the two station use the network at the same time the st1 lost about 80% of its bit rate because of the st1 wifi card thx in advance

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  • Is it common practice to hire third parties to do code reviews for contractors?

    - by blueberryfields
    I recently observed some contract offers which included a "code review by third party" clause - the contract would not pay out fully until the code review was completed and it received a pass. I was surprised, especially considering that these were fairly simple, and small-scale contracts (churning out vanity apps for the iPhone). Is this kind of third-party code review a common thing to run into when contracting out as a programmer?

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  • Stairway to XML: Level 5 - The XML exist() and nodes() Methods

    The XML exist() method is used, often in a WHERE clause, to check the existence of an element within an XML document or fragment. The nodes() method lets you shred an XML instance and return the information as relational data. 12 essential tools for database professionalsThe SQL Developer Bundle contains 12 tools designed with the SQL Server developer and DBA in mind. Try it now.

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  • Graph data structures and journal format for mini-IDE

    - by matec
    Background: I am writing a small/partial IDE. Code is internally converted/parsed into a graph data structure (for fast navigation, syntax-check etc). Functionality to undo/redo (also between sessions) and restoring from crash is implemented by writing to and reading from journal. The journal records modifications to the graph (not to the source). Question: I am hoping for advice on a decision on data-structures and journal format. For the graph I see two possible versions: g-a Graph edges are implemented in the way that one node stores references to other nodes via memory address g-b Every node has an ID. There is an ID-to-memory-address map. Graph uses IDs (instead of addresses) to connect nodes. Moving along an edge from one node to another each time requires lookup in ID-to-address map. And also for the journal: j-a There is a current node (like current working directory in a shell + file-system setting). The journal contains entries like "create new node and connect to current", "connect first child of current node" (relative IDs) j-b Journal uses absolute IDs, e.g. "delete edge 7 - 5", "delete node 5" I could e.g. combine g-a with j-a or combine g-b with j-b. In principle also g-b and j-a should be possible. [My first/original attempt was g-a and a version of j-b that uses addresses, but that turned out to cause severe restrictions: nodes cannot change their addresses (or journal would have to keep track of it), and using journal between two sessions is a mess (or even impossible)] I wonder if variant a or variant b or a combination would be a good idea, what advantages and disadvantages they would have and especially if some variant might be causing troubles later.

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  • Should we encourage coding styles in favor of developer's autonomy, or discourage it in favor of consistency?

    - by Saeed Neamati
    A developer writes if/else blocks with one-line code statements like: if (condition) // Do this one-line code else // Do this one-line code Another uses curly braces for all of them: if (condition) { // Do this one-line code } else { // Do this one-line code } A developer first instantiates an object, then uses it: HelperClass helper = new HelperClass(); helper.DoSomething(); Another developer instantiates and uses the object in one line: new HelperClass().DoSomething(); A developer is more easy with arrays, and for loops: string[] ordinals = new string[] {'First', 'Second', 'Third'}; for (i = 0; i < ordinals.Length; i++) { // Do something } Another writes: List<string> ordinals = new List<string>() {'First', 'Second', 'Third'}; foreach (string ordinal in ordinals) { // Do something } I'm sure that you know what I'm talking about. I call it coding style (cause I don't know what it's called). But whatever we call it, is it good or bad? Does encouraging it have an effect of higher productivity of developers? Should we ask developers to try to write code the way we tell them, so to make the whole system become style-consistent?

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  • Quickbooks Error - Can't turn off auto updates

    - by Murtez
    My company uses quickbooks pro 2002 and unfortunately they won't upgrade at this time, the program keeps freezing and giving methe error: This action cannot be completed because this program is busy.. Then asks to switch or retry, I tracked it down to being an issue with IE since it's an old program and can't use the new versions of IE (the program uses IE for it's interface for some STUPID reason). Everyone says to disable auto updates but the problem is that I can't get to the options area to disable the updates (the options area uses IE!!!) so I'm screwed, I have to sit there and click retry 40-50 times several times a day and it's driving me nutz. I've been looking online for days but have not found a solution to this predicament. Is there a way to disable auto updates through the configuration files? Any help is greatly appreciated.

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  • Tricky situation with EF and Include while projecting (Select / SelectMany)

    - by Vincent Grondin
    Originally posted on: http://geekswithblogs.net/vincentgrondin/archive/2014/06/07/tricky-situation-with-ef-and-include-while-projecting-select.aspxHello, the other day I stumbled on a problem I had a while back with EF and Include method calls and decided this was it and I was going to blog about it…  This would sort of to pin it inside my head and maybe help others too !  So I was using DBContext and wanted to query a DBSet and include some of it’s associations and in the end, do a projection to get a list of Ids…   At first it seems easy…  Query your DBSet, call Include right afterward, then code the rest of your statement with the appropriate where clause and then, do the projection…   Well it wasn’t that easy as my query required I code my where on some entities a few degree further in the association chain and most of these links where “Many”…  I had to do my projection right away with the SelectMany method.  So I did my stuff and tested the query….  no association where loaded…  My Include statement was simply ignored !  Then I remembered this behavior and how to get it to work…  You need to move the Include AFTER your first projection (Select or SelectMany).  So my sequence became:   Query the DBSet, do the projection with SelectMany, Include the associations, code the where clause and do the final projection…. but it wouldn’t compile…   It kept saying that it could not find an “Include” method on an IQueryable… which is perfectly true!  I knew this should work so I went to the definition of the DBset and saw it inherited DBQuery and sure enough the include method was there…  So I had to cast my statement from start until the end of the first projection in a DBQuery then do the Includes and then the rest of my query….   Bottom line is, whenever your Include statement seem to be ignored, then maybe you will need to move them further down in your query and cast your statement in whatever class gives you access to the Include…   Happy coding all !

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  • How do networking ports work? Can I configure the ports that client and server use?

    - by joedotnot
    Let's say i have a "server" program listening on address 1.2.3.4:69 (i.e. remote port 69) When i connect from a "client" program to it, typically i would specify the IP address + port of the target or server system; But what port would the client be using ? And how does the server know which port to connect back to the client on? I understand this question is very general, but just wanting to get a general feel for how things work. Then extending this to a specific protocol, say FTP (typical port 21), can I change it such that the server uses port 69, but the client uses port 100? And similarly, for Remote Desktop in WinXP (typical port 3389), i know how to change the server port to be something other than 3389, but how does one change what port the client uses (if at all possible)?

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  • Correct way to inject dependencies in Business logic service?

    - by Sri Harsha Velicheti
    Currently the structure of my application is as below Web App -- WCF Service (just a facade) -- Business Logic Services -- Repository - Entity Framework Datacontext Now each of my Business logic service is dependent on more than 5 repositories ( I have interfaces defined for all the repos) and I am doing a Constructor injection right now(poor mans DI instead of using a proper IOC as it was determined that it would be a overkill for our project). Repositories have references to EF datacontexts. Now some of the methods in the Business logic service require only one of the 5 repositories, so If I need to call that method I would end up instantiating a Service which will instatiate all 5 repositories which is a waste. An example: public class SomeService : ISomeService { public(IFirstRepository repo1, ISecondRepository repo2, IThirdRepository repo3) {} // My DoSomething method depends only on repo1 and doesn't use repo2 and repo3 public DoSomething() { //uses repo1 to do some stuff, doesn't use repo2 and repo3 } public DoSomething2() { //uses repo2 and repo3 to do something, doesn't require repo1 } public DoSomething3() { //uses repo3 to do something, doesn't require repo1 and repo2 } } Now if my I have to use DoSomething method on SomeService I end up creating both IFirstRepository,ISecondRepository and IThirdRepository but using only IFirstRepository, now this is bugging me, I can seem to accept that I am un-necessarily creating repositories and not using them. Is this a correct design? Are there any better alternatives? Should I be looking at Lazy instantiation Lazy<T> ?

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