What is the best practice for handling exceptions when using command binding in WPF?

Question

I am using the MVVM pattern for a WPF application. In several places I bind commands to input elements in the views as in the following XAML:

Answer 1

The easiest answer is to simply pop a message box. A more sophisticated approach might be to use a notification service, which displays the message to the user in a manner appropiate to you app, but can be mocked out with a fake service for unit testing.