private void PlaySlideShow(Panel panel)
 {
     if (!_playing)
     {
         _playing = true;
         panel.Animate("SlideAnimation", new Animation(), length: 2000, finished: (v, c) => { if (_playing)
                                                                                              {
                                                                                                  InternalPlaySlideShow(panel);
                                                                                              }
                       }, repeat: () => _playing);
     }
     else
     {
         _playing = false;
         panel.AbortAnimation("SlideAnimation");
     }
     OnPropertyChanged("PlayState");
 }