CommandManager.InvalidateRequerySuggested() isn't fast enough. What can I do?

Question

Short Version

Calls to CommandManager.InvalidateRequerySuggested() take far longer to take effect than I would like (1-2 second delay

Answer 1

Tomas has a nice solution, but pls note there's a serious bug in that the CanExecute will not always fire when bound to a Button due to this :

// Call the handlers that we snapshotted
for (int i = 0; i < count; i++)
{
            EventHandler handler = callees[i];
            handler(null, EventArgs.Empty);
}

The 'null' parameter passed in causes issues with the CanExecuteChangedEventManager (used by the WPF Button class to listen to changes on any Command bound to it). Specifically, the CanExecuteChangedEventManager maintains a collection of weak events that need to be invoked to determine if the command Can-Execute() but this collection is keyed by the 'sender'.

The fix is simple and works for me - change the signature to

internal static void CallWeakReferenceHandlers(ICommand sender, List handlers)
{
....
           handler(sender, EventArgs.Empty);
 }

Sorry I haven't described it too well - in a bit of a rush to catch up with my dev now after taking a few hours to figure this out !