Memory leak in WPF app due to DelegateCommand

Question

I just finished desktop apps written in WPF and c# using MVVM pattern. In this app I used Delegate Command implementation to wrap the ICommands properties exposed in my ModelVie

Answer 1

After reading this post, I then came across a web page that had some relating information. It is a page on CodePlex called Memory Leak caused by DelegateCommand.CanExecuteChanged Event.

Reported by : huetter
Updated by : dschenkelman

When profiling my application I noticed that plenty of EventHandlers had never been deregistered from DelegateCommand's CanExecuteChanged-Event. So those EventHandlers were never been garbage-collector, which caused a severe memory leak.

As registering CanExecuteChanged-EventHandles is done outside application code scope I had expected them to be deregistered automatically as well. At this point I thought this might as well be a ThirdParty WPF control issue, but digging further I read a blog post stating that "WPF expects the ICommand.CanExecuteChanged-Event to apply WeakReferences for EventHandlers". I had a look into RoutedCommand, and noticed it uses WeakReferences as well.

I adapted DelegateCommand to use an implementation similar to RoutedCommand's CanExecuteChanged-Event, and the memory leak was gone. The same is true for CompositeCommand.

Closed Nov 3, 2009 at 6:28 PM by This issue was fixed in the Prism-v2.1 release, so the Workitem is closed now. Prism 2.1 can be downloaded from here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=387c7a59-b217-4318-ad1b-cbc2ea453f40&displaylang=en