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  • How to review code that you do not understand?

    - by John Isaacks
    I have been given the role to improve development in our company. The first thing I wanted to start was code reviews since that has never been done here before. There are 3 programmers in our company. I am a web programmer, my known languages are mainly PHP, ActionScript and JavaScript. The other 2 developers write internal applications in VB.net We have been doing code reviews for a couple weeks now. I find it hard to understand VB code. So when they say what its doing, for the most part I just have to take their word for it. If I do see something that looks wrong, I explain my opinion and I explain how I would address it in one of the languages I know. Sometimes my suggestions are welcomed but many times I am told things like "this is the best way of doing it in this language" or "that doesn't apply to this language" or similar things of that nature. This may be true, but without knowing the language I am not sure how to confirm or refute these claims. I know one possible solution would be to learn vb so I can do better code reviews. I really have no interest in learning vb (especially since I have a list of other technologies I am trying to learn for my own projects) and would like to keep this as a last resort but it is an option. Another idea that came to me is, they both have interest in C# and so do I. Its relative to them because its .net and relative to me because its more similar to the languages I know. Yet it is new to all of us. I thought about the benefits of us all collaborating on a pet C#.net project and reviewing each others code from that. I guess theres also the possibility hiring a consultant to come in and give us some code reviews. What would you recommend I do in this situation.

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  • How do you use blank lines in your code ?

    - by Matthieu M.
    There has been a few remarks about white space already in discussion about curly braces placements. I myself tend to sprinkle my code with blank lines in an attempt to segregate things that go together in "logical" groups and hopefully make it easier for the next person to come by to read the code I just produced. In fact, I would say I structure my code like I write: I make paragraphs, no longer than a few lines (definitely shorter than 10), and try to make each paragraph self-contained. For example: in a class, I will group methods that go together, while separating them by a blank line from the next group. if I need to write a comment I'll usually put a blank line before the comment in a method, I make one paragraph per step of the process All in all, I rarely have more than 4/5 lines clustered together, meaning a very sparse code. I don't consider all this white space a waste because I actually use it to structure the code (as I use the indentation in fact), and therefore I feel it worth the screen estate it takes. For example: for (int i = 0; i < 10; ++i) { if (i % 3 == 0) continue; array[i] += 2; } I consider than the two statements have clear distinct purposes and thus deserve to be separated to make it obvious. So, how do you actually use (or not) blank lines in code ?

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  • How do you structure your shared code so that it is "re-findable" for new developers?

    - by awmckinley
    I started working at my current job about 8 months ago, and its been one of the best experiences I've had as a young programmer. It's a small company, and both my co-developers are brilliant guys. One of the practices that they both have been encouraging is lots of code-reuse. Our code base is mainly C#, and we're using a centralized revision control system. The way the repository is currently structured, there is a single folder in which all shared class libraries are placed (along with unit tests for each library), and our revision control system allows for sharing or linking those libraries out to other projects. What I'm trying to understand at this point is how the current structure of the folder can be made more conducive for finding those libraries again. I've talked to the other developers about this, and they agree that it's gotten a little messy. I find that I am sometimes "reinventing the wheel" because I didn't realize that there was an existing piece of code that solved a particular problem. The issue is complicated further by the fact that we're sharing some code between ASP.NET MVC2, WinForms, and Windows CE projects, and sharing code between applications built against multiple versions of .NET. How do other people approach this? Is the answer in naming the libraries in a certain way or is it preferable to invest in some code-search software? Is the answer in doc comments? Should we be sharing libraries at all or should we simply branch the class libraries for re-use? Thanks for any and all help!

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  • How to get feedback from the community on large chunks of code?

    - by MainMa
    Code Review.SE is great when you need feedback on a precise, short piece of code. But where to get similar feedback about the code itself when: you have thousands of LOC, don't have colleagues in your workplace ready or willing to review the code¹, don't have thousands of dollars to spend for a professional review by a third party developer?² Places like CodePlex are a good idea to get your project known³, but from what I've seen, the feedback you get on known projects are consumer feedback, i.e. concerns the bugs and feature requests, not the quality of the source code itself. What are the social way to get the community involved in the code review of the codebase of a certain size for an open source project which doesn't have the scale of Firefox or similar products? ¹ Which is the case for most personal and open source projects, or projects done in companies where the practice of regular and complete code review is nonexistent. ² Which is, again, the case for most personal and open source projects. ³ Even if too many projects published on CodePlex never get known, either because nobody cares or because they are presented not very well.

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  • Does it make sense to write tests for legacy code when there is no time for a complete refactoring?

    - by is4
    I usually try to follow the advice of the book Working Effectively with Legacy Code. I break dependencies, move parts of the code to @VisibleForTesting public static methods and to new classes to make the code (or at least some part of it) testable. And I write tests to make sure that I don't break anything when I'm modifying or adding new functions. A colleague says that I shouldn't do this. His reasoning: The original code might not work properly in the first place. And writing tests for it makes future fixes and modifications harder since devs have to understand and modify the tests too. If it's GUI code with some logic (~12 lines, 2-3 if/else block, for example), a test isn't worth the trouble since the code is too trivial to begin with. Similar bad patterns could exist in other parts of the codebase, too (which I haven't seen yet, I'm rather new); it will be easier to clean them all up in one big refactoring. Extracting out logic could undermine this future possibility. Should I avoid extracting out testable parts and writing tests if we don't have time for complete refactoring? Is there any disadvantage to this that I should consider?

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  • I can't add PPA repository behind the proxy (with @ in the username)

    - by kenorb
    I'm trying to add the ppa repository (as a root) with the following command: export HTTP_PROXY="http://[email protected]:[email protected]:8080" add-apt-repository ppa:nilarimogard/webupd8 Traceback (most recent call last): File "/usr/bin/add-apt-repository", line 125, in <module> ppa_info = get_ppa_info_from_lp(user, ppa_name) File "/usr/lib/python2.7/dist-packages/softwareproperties/ppa.py", line 84, in get_ppa_info_from_lp curl.perform() pycurl.error: (56, 'Received HTTP code 407 from proxy after CONNECT') Unfortunately it doesn't work. Looks like curl is connecting to the proxy, but the proxy says that Authentication is Required. I've tried with .curlrc, http_proxy env instead, but it doesn't work. strace -e network,write -s1000 add-apt-repository ppa:nilarimogard/webupd8 socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP) = 4 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(8080), sin_addr=inet_addr("165.x.x.232")}, 16) = -1 EINPROGRESS (Operation now in progress) getsockopt(4, SOL_SOCKET, SO_ERROR, [0], [4]) = 0 getpeername(4, {sa_family=AF_INET, sin_port=htons(8080), sin_addr=inet_addr("165.x.x.232")}, [16]) = 0 getsockname(4, {sa_family=AF_INET, sin_port=htons(46025), sin_addr=inet_addr("161.20.75.220")}, [16]) = 0 sendto(4, "CONNECT launchpad.net:443 HTTP/1.1\r\nHost: launchpad.net:443\r\nUser-Agent: PycURL/7.22.0\r\nProxy-Connection: Keep-Alive\r\nAccept: application/json\r\n\r\n", 146, MSG_NOSIGNAL, NULL, 0) = 146 recvfrom(4, "HTTP/1.1 407 Proxy Authentication Required\r\nProxy-Authenticate: BASIC realm=\"proxy\"\r\nCache-Control: no-cache\r\nPragma: no-cache\r\nContent-Type: text/html; charset=utf-8\r\nProxy-Connection: close\r\nSet-Cookie: BCSI-CS-91b9906520151dad=2; Path=/\r\nConnection: close\ Maybe it's because there is @ sign in the username? Wget works with proxy fine. Related: How do I add a repository from behind a proxy? Environment Ubuntu 12.04 curl 7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3 curl Features: GSS-Negotiate IDN IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP

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  • Printing problem in Silverlight 4.0 RC - loading images in code behind

    - by Jacek Ciereszko
    Few days ago I faced a problem with printing in new Silverlight 4 RC. When you try to dynamically load image (in code behind) and print it, it doesn't work. Paper sheet is blank. Problem XAML file: <Image x:Name="image" Stretch="None" /> XAML.cs: image.Source = new BitmapImage(new Uri(imageUri, UriKind.RelativeOrAbsolute));  Print: var pd = new PrintDocument();   pd.PrintPage += (s, args) =>     {       args.PageVisual = image;     };   pd.Print(); Result: Blank paper.   Solution What you need to do, is forced Silverlight engine to load that image before printing start. To accomplish that I proposed simply checking PixelWith value. Your code will ask about PixelWidth of image so it will have to be loaded. XAML.cs: BitmapImage bImage = new BitmapImage(new Uri(imageUri, UriKind.RelativeOrAbsolute)); image.Source = bImage; InitControl(imageUri, movieUri, isLeft); int w = bImage.PixelWidth; int h = bImage.PixelHeight;   DONE!   Jacek Ciereszko

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  • OpenVPN, Server 12.04, connect to machines in home LAN behind VPN server

    - by inexion
    Problem: I've set up a working OpenVPN server, and am able to connect to it from anywhere using my mac laptop and tunnelblick. When I connect in, I'm assigned an IP address of 10.8.0.x, the server is 10.8.0.1, so I have no problems SSHing into it. Once SSHd in, I can even ping other machines (obviously) on my home network (192.168.1.x). Desired outcome: What I want, is, to connect to the VPN server, and instead of getting a 10.8.0.x address, I get a 192.168.1.x on my home network. I can't figure out how to talk to the OTHER machines on my home network WITHOUT being SSHd in to the VPN server. I'd like to just connect to my VPN server, then be a part of my home network. Attempted solutions: I've read that I need to set up routes, and/or enable IP forwarding. I enabled IP forwarding using sudo sysctl -w net.ipv4.ip_forward=1 and that doesn't seem to have done anything. I've also uncommented a line in the OpenVPN's server.conf file: # Push routes to the client to allow it # to reach other private subnets behind # the server. Remember that these # private subnets will also need # to know to route the OpenVPN client # address pool (10.8.0.0/255.255.255.0) # back to the OpenVPN server. push "route 192.168.1.0 255.255.255.0" ;push "route 192.168.20.0 255.255.255.0" But still no luck, I still get a 10.8.0.x address... I've also read I may have to add routes to the router itself, but haven't tried that. Any help appreciated, thanks!

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  • Can't complete dropbox installation from behind proxy

    - by Mark Jones
    Problem: My PC on campus sits behind a proxy (requiring authentication) and I can't setup Dropbox. I am convinced that this is a proxy issue as I can't setup Ubuntu one either (but I don't use Ubuntu One so that is not a problem). I have looked at the Ubuntu One fix but it seems to be to modify settings explicitly related to Ubuntu One. I can install the nautilus-dropbox package (compiled from source and from .deb package from website and from software centre) but once I click OK from the "Dropbox Installation" dialog box (prompting me to download the proprietary daemon) the installation just freezes with the OK button pressed. When I look at its process in System Monitor its waiting channel is inet_wait_for_connect. I have set the following proxy directives thus far: Added mj22:**@proxy.waikato.ac.nz:80 information to network proxy settings under network in settings. Added http_host and http_port variables under gconf-editor-system-proxy Added 'host', 'authentication_password' 'authentication_user' and ticked 'user authentication' and 'use_http_proxy' under gconf-editor-system-http_proxy Added export http_proxy="http://mj22:**@proxy.waikato.ac.nz:80/" to /etc/bash.bashrc Added Acquire::http::proxy "http://mj22:**@proxy.waikato.ac.nz:80/"; to /etc/apt/apt.conf (which is what I imagine is letting Software Center retrieve packages). (where ** is my password) I have also added the equivalent ftp and https lines for the above entries. I get the internet fine and Software Centre can download packages but thats it. Related issues: The software centre can't fetch reviews (but can download packages). When trying to add an online account in Gnome 3 a dialog pop up appears with "Error getting a Request Token: Cannot connect to proxy (proxy.waikato.ac.nz)" Updates: After some time (10mins ish) Dropbox shows an error dialog box that reads: Trouble connecting to Dropbox servers. Maybe your internet connection is down, or you need to set you http_proxy environment variable. Is there a way I can see what environment variables are currently set?

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  • Can't complete dropbox installation from behind proxy in Ubuntu 11.10

    - by Mark Jones
    Problem: My PC on campus sits behind a proxy (requiring authentication) and I can't setup Dropbox. I am convinced that this is a proxy issue as I can't setup Ubuntu one either (but I don't use Ubuntu One so that is not a problem). I have looked at the Ubuntu One fix but it seems to be to modify settings explicitly related to Ubuntu One. I can install the nautilus-dropbox package (compiled from source and from .deb package from website and from software centre) but once I click OK from the "Dropbox Installation" dialog box (prompting me to download the proprietary daemon) the installation just freezes with the OK button pressed. When I look at its process in System Monitor its waiting channel is inet_wait_for_connect. I have set the following proxy directives thus far: Added mj22:**@proxy.waikato.ac.nz:80 information to network proxy settings under network in settings. Added http_host and http_port variables under gconf-editor-system-proxy Added 'host', 'authentication_password' 'authentication_user' and ticked 'user authentication' and 'use_http_proxy' under gconf-editor-system-http_proxy Added export http_proxy="http://mj22:**@proxy.waikato.ac.nz:80/" to /etc/bash.bashrc Added Acquire::http::proxy "http://mj22:**@proxy.waikato.ac.nz:80/"; to /etc/apt/apt.conf (which is what I imagine is letting Software Center retrieve packages). (where ** is my password) I have also added the equivalent ftp and https lines for the above entries. I get the internet fine and Software Centre can download packages but thats it. Related issues: The software centre can't fetch reviews (but can download packages). When trying to add an online account in Gnome 3 a dialog pop up appears with "Error getting a Request Token: Cannot connect to proxy (proxy.waikato.ac.nz)" Updates: After some time (10mins ish) Dropbox shows an error dialog box that reads: Trouble connecting to Dropbox servers. Maybe your internet connection is down, or you need to set you http_proxy environment variable. Is there a way I can see what environment variables are currently set?

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  • The Talent Behind Customer Experience

    - by Christina McKeon
    Earlier, I wrote about Powerful Data Lessons from the Presidential Election. A key component of the Obama team’s data analysis deserves its own discussion—the people. Recruiters are probably scrambling to find out who those Obama data crunchers are and lure them into corporations. For the Obama team, these data scientists became a secret ingredient that the competition didn’t have. This team of analysts knew how to hear the signal and ignore the noise, how to segment and target its base, and how to model scenarios and revise plans based on what the data told them. The talent was the difference. As you work to transform your organization to be more customer-centric, don’t forget that talent is a critical element. Journey mapping is a good start to understanding how your talent impacts your customer experiences. Part of journey mapping includes documenting the “on-stage” and “back-stage” systems and touchpoints. When mapping this part of your customers’ journey, include the roles and talent behind the employee actions—both customer facing and further upstream from that customer touchpoint. Know what each of these roles does, how well you are retaining people in these areas, and your plans to fill these open positions in the future. To use data scientists as an example, this job will be in high demand over the next 10 years. The workforce is shrinking, and higher education institutions may not be able to turn out trained data scientists as fast as you need them. You don’t want to be caught with a skills deficit, so consider how you can best plan for the future talent you will need. Have your existing employees make their career aspirations known to you now. You may find you already have employees willing to take on roles that drive better customer experiences. Then develop customer experience talent from within your organization through targeted learning programs. If you know that you will need to go outside the organization, build those candidate relationships now. Nurture the candidates you want to hire and partner with universities, colleges, and trade associations so you can increase the number of qualified candidates in your talent pool.

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  • Using Queries with Coherence Write-Behind Caches

    - by jpurdy
    Applications that use write-behind caching and wish to query the logical entity set have the option of querying the NamedCache itself or querying the database. In the former case, no particular restrictions exist beyond the limitations intrinsic to the Coherence query engine itself. In the latter case, queries may see partially committed transactions (e.g. with a parent-child relationship, the version of the parent may be different than the version of the child objects) and/or significant version skew (the query may see the current version of one object and a far older version of another object). This is consistent with "read committed" semantics, but the read skew may be far greater than would ever occur in a non-cached environment. As is usually the case, the application developer may choose to accept these limitations (with the hope that they are sufficiently infrequent), or they may choose to validate the reads (perhaps via a version flag on the objects). This also applies to situations where a third party application (such as a reporting tool) is querying the database. In many cases, the database may only be in a consistent state after the Coherence cluster has been halted.

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  • Making document storage in Sharepoint a breeze (leave the Web UI behind)

    - by deadlydog
    Hey everyone, I know many of us regularly use Sharepoint for document storage in order to make documents available to several people, have it version controlled, etc.  Doing this through the Web UI can be a real headache, especially when you have multiple documents you want to modify or upload, or when IE isn’t your default browser.  Luckily we can access the Sharepoint library like a regular network drive if we like. Open Sharepoint in Internet Explorer (other browsers don’t support the Open with Explorer functionality), navigate to wherever your documents are stored, choose the Library tab, and then click Open with Explorer. This will open the document storage in Explorer and you can interact with the documents just like they were on any other network drive J  This makes uploading large numbers of documents or directory structures super easy (a simple copy-paste), and modifying your files nice and easy. As an added bonus, you can drag and drop that location from the address bar in Explorer to the Favorites menu so that it’s always easily accessible and you can leave the Sharepoint Web UI behind completely for modifying your documents.  Just click on the new favorite to go straight to your documents.   You can even map this folder location as a network drive if you want to have it show up as another drive (e.g N: drive). I hope you found this as useful as I did

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  • Why is code quality not popular?

    - by Peter Kofler
    I like my code being in order, i.e. properly formatted, readable, designed, tested, checked for bugs, etc. In fact I am fanatic about it. (Maybe even more than fanatic...) But in my experience actions helping code quality are hardly implemented. (By code quality I mean the quality of the code you produce day to day. The whole topic of software quality with development processes and such is much broader and not the scope of this question.) Code quality does not seem popular. Some examples from my experience include Probably every Java developer knows JUnit, almost all languages implement xUnit frameworks, but in all companies I know, only very few proper unit tests existed (if at all). I know that it's not always possible to write unit tests due to technical limitations or pressing deadlines, but in the cases I saw, unit testing would have been an option. If a developer wanted to write some tests for his/her new code, he/she could do so. My conclusion is that developers do not want to write tests. Static code analysis is often played around in small projects, but not really used to enforce coding conventions or find possible errors in enterprise projects. Usually even compiler warnings like potential null pointer access are ignored. Conference speakers and magazines would talk a lot about EJB3.1, OSGI, Cloud and other new technologies, but hardly about new testing technologies or tools, new static code analysis approaches (e.g. SAT solving), development processes helping to maintain higher quality, how some nasty beast of legacy code was brought under test, ... (I did not attend many conferences and it propably looks different for conferences on agile topics, as unit testing and CI and such has a higer value there.) So why is code quality so unpopular/considered boring? EDIT: Thank your for your answers. Most of them concern unit testing (and has been discussed in a related question). But there are lots of other things that can be used to keep code quality high (see related question). Even if you are not able to use unit tests, you could use a daily build, add some static code analysis to your IDE or development process, try pair programming or enforce reviews of critical code.

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • Oops, I left my kernel zone configuration behind!

    - by mgerdts
    Most people use boot environments to move in one direction.  A system starts with an initial installation and from time to time new boot environments are created - typically as a result of pkg update - and then the new BE is booted.  This post is of little interest to those people as no hackery is needed.  This post is about some mild hackery. During development, I commonly test different scenarios across multiple boot environments.  Many times, those tests aren't related to the act of configuring or installing zone and I so it's kinda handy to avoid the effort involved of zone configuration and installation.  A somewhat common order of operations is like the following: # beadm create -e golden -a test1 # reboot Once the system is running in the test1 BE, I install a kernel zone. # zonecfg -z a178 create -t SYSsolaris-kz # zoneadm -z a178 install Time passes, and I do all kinds of stuff to the test1 boot environment and want to test other scenarios in a clean boot environment.  So then I create a new one from my golden BE and reboot into it. # beadm create -e golden -a test2 # reboot Since the test2 BE was created from the golden BE, it doesn't have the configuration for the kernel zone that I configured and installed.  Getting that zone over to the test2 BE is pretty easy.  My test1 BE is really known as s11fixes-2. root@vzl-212:~# beadm mount s11fixes-2 /mnt root@vzl-212:~# zonecfg -R /mnt -z a178 export | zonecfg -z a178 -f - root@vzl-212:~# beadm unmount s11fixes-2 root@vzl-212:~# zoneadm -z a178 attach root@vzl-212:~# zoneadm -z a178 boot On the face of it, it would seem as though it would have been easier to just use zonecfg -z a178 create -t SYSolaris-kz within the test2 BE to get the new configuration over.  That would almost work, but it would have left behind the encryption key required for access to host data and any suspend image.  See solaris-kz(5) for more info on host data.  I very commonly have more complex configurations that contain many storage URIs and non-default resource controls.  Retyping them would be rather tedious.

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  • Using NServiceBus behind a custom web service

    - by Michael Stephenson
    In this post I'd like to talk about an architecture scenario we had recently and how we were able to utilise NServiceBus to help us address this problem. Scenario Cognos is a reporting system used by one of my clients. A while back we developed a web service façade to allow line of business applications to be able to access reports from Cognos to support their various functions. The service was intended to provide access to reports which were quick running reports or pre-generated reports which could be accessed real-time on demand. One of the key aims of the web service was to provide a simple generic interface to allow applications to get any report without needing to worry about the complex .net SDK for Cognos. The web service also supported multi-hop kerberos delegation so that report data could be accesses under the context of the end user. This service was working well for a period of time. The Problem The problem we encountered was that reports were now also required to be available to batch processes. The original design was optimised for low latency so users would enjoy a positive experience, however when the batch processes started to request 250+ concurrent reports over an extended period of time you can begin to imagine the sorts of problems that come into play. The key problems this new scenario caused are: Users may be affected and the latency of on demand reports was significantly slower The Cognos infrastructure was not scaled sufficiently to be able to cope with these long peaks of load From a cost perspective it just isn't feasible to scale the Cognos infrastructure to be able to handle the load when it is only for a couple of hour window each night. We really needed to introduce a second pattern for accessing this service which would support high through-put scenarios. We also had little control over the batch process in terms of being able to throttle its load. We could however make some changes to the way it accessed the reports. The Approach My idea was to introduce a throttling mechanism between the Web Service Façade and Cognos. This would allow the batch processes to push reports requests hard at the web service which we were confident the web service can handle. The web service would then queue these requests and process them behind the scenes and make a call back to the batch application to provide the report once it had been accessed. In terms of technology we had some limitations because we were not able to use WCF or IIS7 where the MSMQ-Activated WCF services could have helped, but we did have MSMQ as an option and I thought NServiceBus could do just the job to help us here. The flow of how this would work was as follows: The batch applications would send a request for a report to the web service The web service uses NServiceBus to send the message to a Queue The NServiceBus Generic Host is running as a windows service with a message handler which subscribes to these messages The message handler gets the message, accesses the report from Cognos The message handler calls back to the original batch application, this is decoupled because the calling application provides a call back url The report gets into the batch application and is processed as normal This approach looks something like the below diagram: The key points are an application wanting to take advantage of the batch driven reports needs to do the following: Implement our call back contract Make a call to the service providing a call back url Provide a correlation ID so it knows how to tie each response back to its request What does NServiceBus offer in this solution So this scenario is not the typical messaging service bus type of solution people implement with NServiceBus, but it did offer the following: Simplified interaction with MSMQ Offered the ability to configure the number of processes working through the queue so we could find a balance between load on Cognos versus the applications end to end processing time NServiceBus offers retries and a way to manage failed messages NServiceBus offers a high availability setup The simple thing is that NServiceBus gave us the platform to build the solution on. We just implemented a message handler which functionally processed a message and we could rely on NServiceBus to do all of the hard work around managing the queues and all of the lower level things that would have took ages to write to any kind of robust level. Conclusion With this approach we were able to deal with a fairly significant performance issue with out too much rework. Hopefully this write up gives people some insight into ideas on how to leverage the excellent NServiceBus framework to help solve integration and high through-put scenarios.

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  • Using the Static Code Analysis feature of Visual Studio (Premium/Ultimate) to find memory leakage problems

    - by terje
    Memory for managed code is handled by the garbage collector, but if you use any kind of unmanaged code, like native resources of any kind, open files, streams and window handles, your application may leak memory if these are not properly handled.  To handle such resources the classes that own these in your application should implement the IDisposable interface, and preferably implement it according to the pattern described for that interface. When you suspect a memory leak, the immediate impulse would be to start up a memory profiler and start digging into that.   However, before you follow that impulse, do a Static Code Analysis run with a ruleset tuned to finding possible memory leaks in your code.  If you get any warnings from this, fix them before you go on with the profiling. How to use a ruleset In Visual Studio 2010 (Premium and Ultimate editions) you can define your own rulesets containing a list of Static Code Analysis checks.   I have defined the memory checks as shown in the lists below as ruleset files, which can be downloaded – see bottom of this post.  When you get them, you can easily attach them to every project in your solution using the Solution Properties dialog. Right click the solution, and choose Properties at the bottom, or use the Analyze menu and choose “Configure Code Analysis for Solution”: In this dialog you can now choose the Memorycheck ruleset for every project you want to investigate.  Pressing Apply or Ok opens every project file and changes the projects code analysis ruleset to the one we have specified here. How to define your own ruleset  (skip this if you just download my predefined rulesets) If you want to define the ruleset yourself, open the properties on any project, choose Code Analysis tab near the bottom, choose any ruleset in the drop box and press Open Clear out all the rules by selecting “Source Rule Sets” in the Group By box, and unselect the box Change the Group By box to ID, and select the checks you want to include from the lists below. Note that you can change the action for each check to either warning, error or none, none being the same as unchecking the check.   Now go to the properties window and set a new name and description for your ruleset. Then save (File/Save as) the ruleset using the new name as its name, and use it for your projects as detailed above. It can also be wise to add the ruleset to your solution as a solution item. That way it’s there if you want to enable Code Analysis in some of your TFS builds.   Running the code analysis In Visual Studio 2010 you can either do your code analysis project by project using the context menu in the solution explorer and choose “Run Code Analysis”, you can define a new solution configuration, call it for example Debug (Code Analysis), in for each project here enable the Enable Code Analysis on Build   In Visual Studio Dev-11 it is all much simpler, just go to the Solution root in the Solution explorer, right click and choose “Run code analysis on solution”.     The ruleset checks The following list is the essential and critical memory checks.  CheckID Message Can be ignored ? Link to description with fix suggestions CA1001 Types that own disposable fields should be disposable No  http://msdn.microsoft.com/en-us/library/ms182172.aspx CA1049 Types that own native resources should be disposable Only if the pointers assumed to point to unmanaged resources point to something else  http://msdn.microsoft.com/en-us/library/ms182173.aspx CA1063 Implement IDisposable correctly No  http://msdn.microsoft.com/en-us/library/ms244737.aspx CA2000 Dispose objects before losing scope No  http://msdn.microsoft.com/en-us/library/ms182289.aspx CA2115 1 Call GC.KeepAlive when using native resources See description  http://msdn.microsoft.com/en-us/library/ms182300.aspx CA2213 Disposable fields should be disposed If you are not responsible for release, of if Dispose occurs at deeper level  http://msdn.microsoft.com/en-us/library/ms182328.aspx CA2215 Dispose methods should call base class dispose Only if call to base happens at deeper calling level  http://msdn.microsoft.com/en-us/library/ms182330.aspx CA2216 Disposable types should declare a finalizer Only if type does not implement IDisposable for the purpose of releasing unmanaged resources  http://msdn.microsoft.com/en-us/library/ms182329.aspx CA2220 Finalizers should call base class finalizers No  http://msdn.microsoft.com/en-us/library/ms182341.aspx Notes: 1) Does not result in memory leak, but may cause the application to crash   The list below is a set of optional checks that may be enabled for your ruleset, because the issues these points too often happen as a result of attempting to fix up the warnings from the first set.   ID Message Type of fault Can be ignored ? Link to description with fix suggestions CA1060 Move P/invokes to NativeMethods class Security No http://msdn.microsoft.com/en-us/library/ms182161.aspx CA1816 Call GC.SuppressFinalize correctly Performance Sometimes, see description http://msdn.microsoft.com/en-us/library/ms182269.aspx CA1821 Remove empty finalizers Performance No http://msdn.microsoft.com/en-us/library/bb264476.aspx CA2004 Remove calls to GC.KeepAlive Performance and maintainability Only if not technically correct to convert to SafeHandle http://msdn.microsoft.com/en-us/library/ms182293.aspx CA2006 Use SafeHandle to encapsulate native resources Security No http://msdn.microsoft.com/en-us/library/ms182294.aspx CA2202 Do not dispose of objects multiple times Exception (System.ObjectDisposedException) No http://msdn.microsoft.com/en-us/library/ms182334.aspx CA2205 Use managed equivalents of Win32 API Maintainability and complexity Only if the replace doesn’t provide needed functionality http://msdn.microsoft.com/en-us/library/ms182365.aspx CA2221 Finalizers should be protected Incorrect implementation, only possible in MSIL coding No http://msdn.microsoft.com/en-us/library/ms182340.aspx   Downloadable ruleset definitions I have defined three rulesets, one called Inmeta.Memorycheck with the rules in the first list above, and Inmeta.Memorycheck.Optionals containing the rules in the second list, and the last one called Inmeta.Memorycheck.All containing the sum of the two first ones.  All three rulesets can be found in the  zip archive  “Inmeta.Memorycheck” downloadable from here.   Links to some other resources relevant to Static Code Analysis MSDN Magazine Article by Mickey Gousset on Static Code Analysis in VS2010 MSDN :  Analyzing Managed Code Quality by Using Code Analysis, root of the documentation for this Preventing generated code from being analyzed using attributes Online training course on Using Code Analysis with VS2010 Blogpost by Tatham Oddie on custom code analysis rules How to write custom rules, from Microsoft Code Analysis Team Blog Microsoft Code Analysis Team Blog

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  • Stand-alone Java code formatter/beautifier/pretty printer?

    - by Greg Mattes
    I'm interested in learning about the available choices of high-quality, stand-alone source code formatters for Java. The formatter must be stand-alone, that is, it must support a "batch" mode that is decoupled from any particular development environment. Ideally it should be independent of any particular operating system as well. So, a built-in formatter for the IDE du jour is of little interest here (unless that IDE supports batch mode formatter invocation, perhaps from the command line). A formatter written in closed-source C/C++ that only runs on, say, Windows is not ideal, but is somewhat interesting. To be clear, a "formatter" (or "beautifier") is not the same as a "style checker." A formatter accepts source code as input, applies styling rules, and produces styled source code that is semantically equivalent to the original source code. A style checker also applies styling rules, but it simply reports rule violations without producing modified source code as output. So the picture looks like this: Formatter (produces modified source code that conforms to styling rules) Read Source Code → Apply Styling Rules → Write Styled Source Code Style Checker (does not produce modified source code) Read Source Code → Apply Styling Rules → Write Rule Violations Further Clarifications Solutions must be highly configurable. I want to be able to specify my own style, not simply select from a canned list. Also, I'm not looking for a general purpose pretty-printer written in Java that can pretty-print many things. I want to style Java code. I'm also not necessarily interested in a grand-unified formatter for many languages. I suppose it might be nice for a solution to have support for languages other than Java, but that is not a requirement. Furthermore, tools that only perform code highlighting are right out. I'm also not interested in a web service. I want a tool that I can run locally. Finally, solutions need not be restricted to open source, public domain, shareware, free software, commercial, or anything else. All forms of licensing are acceptable.

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  • Who is code wanderer?

    - by DigiMortal
    In every area of life there are people with some bad habits or misbehaviors that affect the work process. Software development is also not free of this kind of people. Today I will introduce you code wanderer. Who is code wanderer? Code wandering is more like bad habit than serious diagnose. Code wanderers tend to review and “fix” source code in files written by others. When code wanderer has some free moments he starts to open the code files he or she has never seen before and starts making little fixes to these files. Why is code wanderer dangerous? These fixes seem correct and are usually first choice to do when considering nice code. But as changes are made by coder who has no idea about the code he or she “fixes” then “fixing” usually ends up with messing up working code written by others. Often these “fixes” are not found immediately because they doesn’t introduce errors detected by compilers. So these “fixes” find easily way to production environments because there is also very good chance that “fixed” code goes through all tests without any problems. How to stop code wanderer? The first thing is to talk with person and explain him or her why those changes are dangerous. It is also good to establish rules that state clearly why, when and how can somebody change the code written by other people. If this does not work it is possible to isolate this person so he or she can post his or her changes to code repository as patches and somebody reviews those changes before applying them.

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  • What would you add to Code Complete 3rd Edition?

    - by Peter Turner
    It's been quite a few years since Code Complete was published. I really love the book, I keep it in the bathroom at the office and read a little out of it once or twice a day. I was just wondering for the sake of wonderment, what kinds of things need to be added to Code Complete 3e, and for the sake of reductionism, what kinds of things would be removed. Also, what languages would you use for code examples?

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  • How to facilitate code reviews in a small team for embedded software?

    - by Adam Lewis
    Short Question Does a cost-effective tool / workflow exist to facilitate code reviews in a small team? More specifically, a small team that relies on post-commit code reviews. Background Our team currently consists of 3 full time and 1 part time software engineers, with plans on hiring more in the near future. Due to our team size and volume of projects we all must juggle, the pre-commit workflow that major tools (such as Review Board and Code Collaborator) use is not obtainable for us right now. The best we can do at the moment is to perform post-commit reviews before major releases or as time permits. Nearly all of our projects are hosted on RepositoryHosting.com (which I highly recommend) and contain a mixture of SVN and GIT repositories. Current Thoughts Since I cannot find a tool that fits our needs right now, I am turning to TRAC that is built into our repository's site. At the moment we use TRAC to file tickets and track milestones, so to me this seems like a natural fit for code review results as well. The direction I am heading in right now is to use a spread sheet(s) to log all of the bugs and comments. Do some macro magic to get it in a format that I can use TRAC's import ticket method and use TRAC's ticketing system to create the action items / bug reports automatically. The auto ticket generation is darn near a must have, adding in bugs and comments one at a time from a web-gui is really painful. Secondary Question If this workflow makes sense, is there a good / standard template to use as a code review log?

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