Using WPF Validation rules and the disabling of a 'Save' button

Question

I have a page where a few textboxes cannot be empty before clicking a Save button.

Answer 1

int count = 0;

private void LayoutRoot_BindingValidationError(object sender, ValidationErrorEventArgs e)
{
    if (e.Action == ValidationErrorEventAction.Added)
    {
        button1.IsEnabled = false;
        count++;
    }
    if (e.Action == ValidationErrorEventAction.Removed)
    {                
        count--;
        if (count == 0) button1.IsEnabled = true;
    }
}