Parallel MSBuild

Did you know MSBuild can now run your build using all the cores on your proccessor? So if your development machine has multi-cores, and your solution is fairly large (perhaps more than 15 projects, but it varies), and you’re developing in .NET Framework 3.5 or higher, you should give parallel builds a go, and see if there’s any savings in compile time.

Scott Hanselman has 2 great articles on this. He explains how to incorporate parallel builds into Visual Studio, and also talks about how to run parallel build in your build process and scripts.

Take note that it’s not a guarantee that it is always going to make your solution build faster, it also depends on your machine specifications as well as how your project dependency structure. If that structures is linear rather than a tree structure, there would not be much benefit running parallel builds. Also take care about how your project references are used, because running parallel build might cause some unexpected locking problems.

On a more positive note, I’m working on a solution with around 57 projects, and using an 8 core PC. Running parallel build, it shaved off 25 seconds off the usual 2 minutes build. For argument’s sake, if I build my solution say 50 times a time (which is a very optimistic value in my opinion),  I save about  20 minutes a day from compiling (assuming you have an 8 hour work day). That’s a big savings, and that benefit grows over the weeks and months for every developer on your team. Don’t forget your build scripts and automated builds too!


ResourceDictionary: Use with care

Seems like WPF is plagued with memory leaks and problems, if not handled with care. Resource dictionary is another potential pain point, the current project I’m working on is one such victim.

Consider an UserControl that references a ResourceDictionary in it’s MergedDictionaries. Consider that the referenced ResourceDictionary references other ResourceDictionaries, and so on. Now consider that you render 30 of these user controls on a window, each user control creates a unique instance of the same ResourceDictionary, plus much more. Now you suddenly have heaps of memory being allocated, unnecessary memory for that matter. Apparently this occurs in .NET 3.5 only, not 4.0.

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WPF DynamicResource memory leak

After some troubleshooting on WPF memory leaks, I came across a memory leak that occurs when using DynamicResource on resource keys declared in Application.Resources. You can read about this problem being discussed on msdn forum and stackoverflow. To fix this problem, fortunately there’s a patch for .NET 3.5 and .NET 4.0 resolved this issue.

If you’re developing in Silverlight, no issue as there’s no DynamicResource. If you’re developing in WPF, I urge you to consider if there’s a need at all to use DynamicResource. If you’re not using SystemColors, SystemFonts or themes in your application, StaticResource should be considered because DynamicResource are re-evaluated at runtime whenever the resource is requested which is an overhead. If you’re not familiar about their usages, you can read more about them here.

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WPF memory leaks

After working on a WPF application for a couple of months, I’ve noticed that the application was leaking a large chunk of memory. After some memory profiling, the culprit was not very apparent. It seems that it was a combination of issues that contributed to the leak. One of the biggest problem was that data-binding was not done “properly”.

So what do I mean by “data-binding not done properly? Apparently if your DataContext does not implement INotifyPropertyChanged, you’re in big trouble!! Here’s a link from Microsoft that explains the phenomenon….

After much research, I came across a fantastic article explaining all the possible errors one can make to cause a memory leak. Some of these are not WPF inherent problems, they are just typical memory leak culprits dominant in all .NET applications, e.g. failure to unsubscribe an event handler; while some are just obscure and weird. But rest assured that some of the weird ones are fixed in .NET Framework 3.5 SP1 and .NET Framework 4…. So if you develop in WPF, this article is a MUST READ!!!!!

Lastly, a word of caution. Remember to start performance testing and memory profiling quite early in the stages of development. It’s a misconception that these activities can be put off until the late stages. If you do that, you have to bear the consequence of not being able to fix these problems because it becomes too hard to change code and change design…you have been warned.

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