protected override void OnKeyUp(KeyEventArgs e)
 {
     base.OnKeyUp(e);
     if (!(e.Source is TextBox))
     {
         if (Key.Delete == e.Key)
         {
             DesginControl.Delete();
         }
     }
 }
 void DeleteButton_Click(object sender, RoutedEventArgs e)
 {
     DesginControl.Delete();
 }