public override void OnValueChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (!(sender is PasswordBox passwordBox))
{
throw new NotSupportedException($"{nameof(MonitorPasswordProperty)} may only be attached to a PasswordBox");
}
// Remove any previous events
passwordBox.PasswordChanged -= PasswordBox_PasswordChanged;
// If the caller set MonitorPassword to true...
if ((bool)e.NewValue)
{
// Set default value
HasTextProperty.SetValue(passwordBox);
// Start listening out for password changes
passwordBox.PasswordChanged += PasswordBox_PasswordChanged;
}
}