public MapTOCContentType CurrentMapTOCContent {get;}

//Get the current active TOC content type for the map view 
var mapTOCContentType = MapView.Active.CurrentMapTOCContent;

      //Get the current active TOC content type for the map view 
      var mapTOCContentType = (int)MapView.Active.CurrentMapTOCContent;
//increment to the next tab whatever it is
mapTOCContentType++;
//Can we set this type on the TOC?
      if (MapView.Active.CanSetMapTOCContent((MapTOCContentType)mapTOCContentType))
  //Set it - must be on the UI! - No QueuedTask
          MapView.Active.SetMapTOCContentAsync((MapTOCContentType)mapTOCContentType);
else
{
          mapTOCContentType = (int)MapTOCContentType.DrawingOrder;
          //Set it - must be on the UI! - No QueuedTask
          MapView.Active.SetMapTOCContentAsync((MapTOCContentType)mapTOCContentType);
      }