llblgen group by

IGroupByCollection groupingClause = new GroupByCollection();
groupingClause.Add(EmployeePositionFields.ID);
groupingClause.Add(EmployeePositionFields.Name);
groupingClause.HavingClause = new
    PredicateExpression(
         EmployeePositionFields.ID.SetAggregateFunction(AggregateFunction.Count) > 0);