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.
            }
        }
    });
}