/// <summary>
 /// Begins the polling for retrieving markers.
 /// </summary>
 public override void BeginRetrievingMarkers()
 {
     if (!IsRetrievingMarkers)
     {
         _request.StartPolling();
         IsRetrievingMarkers = _request.IsDownloading;
         if (IsRetrievingMarkers)
         {
             base.BeginRetrievingMarkers();
         }
     }
 }
 /// <summary>
 /// Begins the polling for retrieving markers.
 /// </summary>
 public void BeginRetrievingMarkers()
 {
     _request.StartPolling();
 }