static void RightButtonDownShow(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            UIElement element      = (UIElement)sender;
            Window    targetWindow = element.GetValue(TargetWindow) as Window;
            Point     showMenuAt   = targetWindow.PointToScreen(Mouse.GetPosition((targetWindow)));

            SystemMenuManager.ShowMenu(targetWindow, showMenuAt);
        }
 static void LeftButtonDownShow(object sender, MouseButtonEventArgs e)
 {
     if (leftButtonToggle)
     {
         object element      = ((UIElement)sender).GetValue(LeftButtonShowAt);
         Point  showMenuAt   = ((Visual)element).PointToScreen(new Point(0, 0));
         Window targetWindow = ((UIElement)sender).GetValue(TargetWindow) as Window;
         SystemMenuManager.ShowMenu(targetWindow, showMenuAt);
         leftButtonToggle = !leftButtonToggle;
     }
     else
     {
         leftButtonToggle = !leftButtonToggle;
     }
 }