public void DeletePlaylist(PlaylistItem p)
 {
     if (p.IsSmart)
     {
         if (ApplicationSettingsHelper.PredefinedSmartPlaylistsId().ContainsKey(p.Id))
         {
         }
         else
         {
             Playlists.Remove(p);
             DatabaseManager.DeleteSmartPlaylist(p.Id);
         }
     }
     else
     {
         Playlists.Remove(p);
         DatabaseManager.DeletePlainPlaylist(p.Id);
     }
 }