MVVM RelayCommand CanExecute

For some reason you have to do the following:

public RelayCommand RedoCommand{
     get;
     set;
}

you can also put private before set optional, depending on your access level. Then you do

RedoCommand = new RelayCommand(() => undoRedoController.Redo(), () => undoRedoController.CanRedo());

Now your able to call RedoCommand.RaiseCanExecuteChanged(); And everything works.

There has been a hiatus with MVVMLight due to the fact that after the .NET 4.5 update the CommandManager no longer fires the can execute check. This has since been solved. Instead of including the GalaSoft.MvvmLight.Command namespace you should use the GalaSoft.MvvmLight.CommandWpf namespace. The RelayCommand defined in that namespace is still checking the CanExecute function that you pass to the command.

Took me about a day to find out what the hell was going wrong in my application. I hope this will help some of you.

Here is a blog post by the developer explanining why this is necessary.

If you are using an unpatched .net 4.5. Microsoft broke the .CanExecute event.

http://connect.microsoft.com/VisualStudio/feedback/details/753666/net-4-0-application-commands-canexecute-not-updating-in-4-5

If you are using the RelayCommand from http://msdn.microsoft.com/en-us/magazine/dd419663.aspx#id0090030 and are not raising the CanExecuteChanged event when redoStack changes.