private void this_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            VideoControlViewModel oldVM = e.OldValue as VideoControlViewModel;
            VideoControlViewModel newVM = e.NewValue as VideoControlViewModel;

            if (oldVM != null)
            {
                oldVM.PropertyChanged -= model_PropertyChanged;
            }
            if (newVM != null)
            {
                newVM.PropertyChanged += model_PropertyChanged;
            }
        }
 private void PlayCtrl_VideoAdded(Video.VideoControlViewModel obj)
 {
     updateDisplayVideos();
 }