private void createVideoWindow()
 {
     videoWindow = new second(this);
     videoWindow.WindowStartupLocation = System.Windows.WindowStartupLocation.Manual;
     videoWindow.Top      = 10;
     videoWindow.Left     = 10;
     videoWindow.Topmost  = true;
     videoWindow.Closing += new CancelEventHandler(this.OnWindowClosing);
 }
 public void OnWindowClosing(object sender, CancelEventArgs e)
 {
     this.videoWindow = null;
 }