void _downloader_DownloadingImageEvent(object sender, DownloadingImageEventArgs e)
 {
     App.Current.Dispatcher.BeginInvoke(((Action)(() =>
         JobActivityGroups.Insert(0, new JobActivityGroupViewModel(this, e.ParentActivity, e.Downloader)))));
 }
 protected virtual void OnAddedDownloadingImage(DownloadingImageEventArgs e)
 {
     if (AddedDownloadingImage != null)
         AddedDownloadingImage(this, e);
 }