ICommand CanExecuteChanged not updating

Question

I am trying for MVVM pattern basic level and got struck at ICommand CanExecute changed. I have XAML binding as follows:

Answer 1

As Raul Otaño has pointed out, you can raise the CanExecuteChanged. However, not all MVVM frameworks provide a RaiseCanExecuteChanged method. It's also worth noting that the actual event CanExecuteChanged must be called on the UI thread. So, if you're expecting a callback from some thread in your model, you need to invoke it back to the UI thread, like this:

    public void RaiseCanExecuteChanged()
    {
        if (CanExecuteChanged != null)
        {
            Application.Current.Dispatcher.Invoke((Action)(() => { CanExecuteChanged(this, EventArgs.Empty); }));
        }
    }

I would very much recommend against calling CommandManager.InvalidateRequerySuggested() because although this works functionally, and is ok for small applications, it is indiscriminate and will potentially re-query every command! In a large system with lots of commands, this can be very very slow!