public void SetObjectIDFields( 
   string objectIDFields
)

public async Task JoinQueryDescription()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    DatabaseConnectionProperties databaseConnectionProperties = 
    new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
    {
      AuthenticationMode = AuthenticationMode.DBMS,
      Instance = "instance",
      Database = "database",
      User = "user",
      Password = "password"
    };

    using (Database database = new Database(databaseConnectionProperties))
    {
      QueryDescription queryDescription = database.GetQueryDescription("SELECT BUSLINES.ID as BUSLINESID, BUSSTOPS.ID as BUSSTOPSID, BUSLINES.RTE_DESC, BUSLINES.DIR, BUSSTOPS.JURISDIC, BUSSTOPS.LOCATION, BUSSTOPS.ROUTE,BUSSTOPS.SHAPE from demosql.dbo.BUSSTOPS JOIN demosql.dbo.BUSLINES ON BUSSTOPS.ROUTE = BUSLINES.ROUTE", "BusInfo");

      queryDescription.SetObjectIDFields("BUSLINESID,BUSSTOPSID");

      using (Table table = database.OpenTable(queryDescription))
      {
        // Use the table.
      }
    }
  });
}