ArcGIS Pro 3.4 API Reference Guide
ArcGIS.Core.Data.Realtime Namespace / RealtimeFeatureClass Class / Subscribe Method
A null query filter will cause all rows that become available to be retrieved.
If set to true, all the entries in RealtimeCursor will reference the most current row returned by RealtimeCursor.Current. To ensure all the entries in RealtimeCursor remain unique, set useRecyclingCursor to false. The default is true.
Example

In This Topic
    Subscribe Method (RealtimeFeatureClass)
    In This Topic
    Subscribe to receive row events. This method must be called on the MCT. Use QueuedTask.Run.
    Syntax

    Parameters

    queryFilter
    A null query filter will cause all rows that become available to be retrieved.
    useRecyclingCursor
    If set to true, all the entries in RealtimeCursor will reference the most current row returned by RealtimeCursor.Current. To ensure all the entries in RealtimeCursor remain unique, set useRecyclingCursor to false. The default is true.

    Return Value

    A RealtimeCursor that encapsulates the retrieved rows, as well as provides facilities to wait for new row events.
    Exceptions
    ExceptionDescription
    A geodatabase-related exception has occurred.
    Remarks
    This method is thread-safe and it can be called on any thread. If the cursor is disposed or in the process of being disposed when this method is called it will result in undefined behavior. As opposed to SearchAndSubscribe, this method does not perform a Search operation. As a consequence, the returned RealtimeCursor will only iterate over rows that became available immediately after the execution of this method. If no query filter is set, all rows that become available will be retrieved.
    Example
    Subscribe to Streaming Data
    //Note: with feature class we can also use a System Task to subscribe and
    //process rows
    await QueuedTask.Run(async () =>
    {
      // or var rfc = realtimeDatastore.OpenTable(name) as RealtimeFeatureClass
      using (var rfc = streamLayer.GetFeatureClass())
      {
        //non-recycling cursor - 2nd param "false"
        //subscribe, pre-existing rows are not searched
        using (var rc = rfc.Subscribe(qfilter, false))
        {
          SpatialQueryFilter spatialFilter = new SpatialQueryFilter();
          //waiting for new features to be streamed
          //default is no cancellation
          while (await rc.WaitForRowsAsync())
          {
            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...
                    countyFeatureLayer.Select(spatialFilter);
                    continue;
                  default:
                    continue;
                }
              }                  
            }
          }
        }//row cursor is disposed. row cursor is unsubscribed
      }
    });
    Search Existing Data and Subscribe for Streaming Data
    //Note we can use System Task with the Realtime feature class
    //for subscribe
    await System.Threading.Tasks.Task.Run(async () =>
    // or use ... QueuedTask.Run()
    {
      using (var rfc = streamLayer.GetFeatureClass())
      {
        //non-recycling cursor - 2nd param "false"
        using (var rc = rfc.SearchAndSubscribe(qfilter, false))
        {
          //waiting for new features to be streamed
          //default is no cancellation
          while (await rc.WaitForRowsAsync())
          {
            //pre-existing rows will be retrieved that were searched
            while (rc.MoveNext())
            {
              using (var row = rc.Current)
              {
                var row_source = row.GetRowSource();
                switch (row_source)
                {
                  case RealtimeRowSource.EventDelete:
                    //TODO - handle deletes
                    break;
                  case RealtimeRowSource.EventInsert:
                    //TODO handle inserts
                    break;
                  case RealtimeRowSource.PreExisting:
                    //TODO handle pre-existing rows
                    break;
                }
              }
            }
          }
        }//row cursor is disposed. row cursor is unsubscribed
      }
    });
    
    Requirements

    Target Platforms: Windows 11, Windows 10

    ArcGIS Pro version: 3 or higher.
    See Also