private void RegisterCommandOrShift(RoutedCommand command, Key key, ModifierKeys modifierKeys = ModifierKeys.None, object commandParameter = null)
 {
     RadRichTextBox.RegisterCommand(command, key, modifierKeys, commandParameter);
     RadRichTextBox.RegisterCommand(command, key, modifierKeys | ModifierKeys.Shift, commandParameter);
 }
 public void RegisterCommand(RoutedCommand command, Key key, ModifierKeys modifierKeys = ModifierKeys.None, object commandParameter = null)
 {
     RadRichTextBox.RegisterCommand(command, key, modifierKeys, commandParameter);
 }