void OnThumbnailAdded(CachedThumbnail t)
 {
     if (ThumbnailAdded != null) ThumbnailAdded(this, t);
 }
 void OnThumbnailRequested(CachedThumbnail t)
 {
     if (ThumbnailRequested != null) ThumbnailRequested(this, t);
 }
 void LoadThumbnail(CachedThumbnail thumbnailToLoad)
 {
     LoadingThumbnails.Add(thumbnailToLoad);
     OnThumbnailRequested(thumbnailToLoad);
     LoadThumbnailAsync(thumbnailToLoad.TimeStamp, thumbnailToLoad);
 }