I cannot tell you exactly what events the CommandManager
listens to. However, I can tell you that you should be careful when using the CommandManager
in connection with asynchronous operations. I had the following problem when I used the CommandManager
in my ICommand
implementations:
I had a button bound to an ICommand
which triggered an asynchronous operation which increased a value. Now, the button/ICommand
should be disabled (i.e. its CanExecute()
method should return false
) if the value had reached a certain limit. The problem was: The CommandManager
called my CanExecute()
method right after the button had been clicked and the asynchronous operation had been started. This asynchronous operation did not take long, but it was long enough to get its result after the CommandManager
's check, so that the limit check in CanExecute()
was done using the old value. Therefore, the button remained enabled although the limit was actually reached. The funny thing was, after you clicked anywhere in the UI, the button now got disabled because the CommandManager
checked the ICommand
once again and now the new value was checked against the limit.
Actually, I think the CommandManager
waited around 50ms after the button click until it performed the check of the ICommand
, but I am not quite sure about that.
My solution was to force the CommandManager
to check the ICommand
again by calling the CommandManager.InvalidateRequerySuggested
method in my ViewModel right after I received the result of the async operation.