In the previous example, you saw how the
ViewModelBase.IsComplete method is used to trigger validation of a viewmodel. This section looks at extending the validation to set control-enabled states based on the presence of validation errors and at hiding validation errors until the user has had a chance to fill out the form.
SendEmailViewModel in the downloadable sample code is a more complex example of asynchronous input validation. In it, the
sendEmailCommand is prevented from executing if it is already in execution or if the form is invalid.
SendEmailView is ...