static void OnCommandChanged(Control sender, AttachedPropertyChangedEventArgs<ICommand> e)
{
Button button = sender as Button;
if(button == null)
return;
UpdateButtonEnabled(button, e.NewValue, GetCommandParameter(button));
button.Click -= OnClick;
if(e.OldValue != null) {
var handler = button.GetValue(HandlerProperty);
e.OldValue.CanExecuteChanged -= handler.Handler;
button.ClearValue(HandlerProperty);
}
if(e.NewValue != null) {
button.Click += OnClick;
var handler = new CanExecuteChangedHandler(button, (b, o, ea) => UpdateButtonEnabled(b, b.GetCommand(), b.GetCommandParameter()));
e.NewValue.CanExecuteChanged += handler.Handler;
button.SetValue(HandlerProperty, handler);
}
}
