public Geometry GetShape()

{
  //Note: with feature class we can also use a System Task to subscribe and
  //process rows
  // Note: call within QueuedTask.Run()
  {
    // or var rfc = realtimeDatastore.OpenTable(name) as RealtimeFeatureClass
    using RealtimeFeatureClass rfc = streamLayer.GetFeatureClass();
    //non-recycling cursor - 2nd param "false"
    //subscribe, pre-existing rows are not searched
    using RealtimeCursor rc = rfc.Subscribe(qfilter, false);
    SpatialQueryFilter spatialFilter = new SpatialQueryFilter();
    //waiting for new features to be streamed
    //default is no cancellation
    while (rc.WaitForRowsAsync().Result)
    {
      while (rc.MoveNext())
      {
        using (var row = rc.Current)
        {
          switch (row.GetRowSource())
          {
            case RealtimeRowSource.EventInsert:
              //getting geometry from new events as they arrive
              Polygon poly = ((RealtimeFeature)row).GetShape() as Polygon;

              //using the geometry to select features from another feature layer
              spatialFilter.FilterGeometry = poly;//project poly if needed...
              featureLayer.Select(spatialFilter);
              continue;
            default:
              continue;
          }
        }
      }
    }
    //row cursor is disposed. row cursor is unsubscribed
  }
}