public void StartStreaming()

{
  var url = "https://geoeventsample1.esri.com:6443/arcgis/rest/services/AirportTraffics/StreamServer";

  // Note: call within QueuedTask.Run()
  {
    var realtimeServiceConProp = new RealtimeServiceConnectionProperties(
                                   new Uri(url),
                                   RealtimeDatastoreType.StreamService
                                );
    using var realtimeDatastore = new RealtimeDatastore(realtimeServiceConProp);
    //A Realtime data store only contains **one** Realtime feature class (or table)
    var name = realtimeDatastore.GetTableNames().First();
    using (RealtimeFeatureClass realtimeFeatureClass = realtimeDatastore.OpenTable(name) as RealtimeFeatureClass)
    {
      //feature class, by default, is not streaming (opposite of the stream layer)
      realtimeFeatureClass.StartStreaming();
      //TODO use the feature class
      //...
    }
  }
}