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);
}