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

In your case, what contains a reference to what?

1. DelegateCommand contains a reference to ViewModel - its execute and canExecute properties contain references to a methods of the ViewModel instance.

2. ViewModel contains a reference to DelegateCommand - its PrintCommand property.

3. The view contains any number of references to the ViewModel.

4. The CommandManager contains a reference to DelegateCommand in its RequerySuggested event.

That last reference is a special case: CommandManager uses a WeakReference in its RequerySuggested event, so despite the fact that DelegateCommand registers for that event, it can still be garbage-collected.

Given all this, you shouldn't be having a problem. If the view gets disposed, neither the ViewModel nor the DelegateCommand should be reachable.

You say you've profiled the application and DelegateCommand is holding a reference to ViewModel. It seems to me that the logical next question should be: what's holding a reference to DelegateCommand? It shouldn't be CommandManager. Do you have something else in your application that's referencing your commands?