internal FeedEntriesViewModel(FeedSourceViewModel p)
 {
   _page = p.Page;
   _parent = p;
   Reload();
 }
 void OnSelectedFeedSourceChanged(FeedSourceViewModel cur)
 {
   if (FeedEntriesViewModel != null)
   {
     FeedEntriesViewModel.Cleanup();
     FeedEntriesViewModel = null;
   }
   if (cur == null)
   {
     return;
   }
   FeedEntriesViewModel = new FeedEntriesViewModel(cur);
 }