llblgen v3, adapter,vb.net

Want to sort by date asc but do not NULLS to be on the top

How do i do this in llblgen

ORDER BY (CASE WHEN [Submission Date] IS NULL THEN 1 ELSE 0 END) DESC, [Submission Date] DESC

Please check sorting on an expression

Any suggestion on how i put this expression into llblgen?

    IExpression datePart = new DbFunctionCall("CASE WHEN {0} IS NULL THEN 1 ELSE 0 END", new object[] { OrdersFields.OrderDate });
    IEntityField2 datePartField = OrdersFields.OrderDate.SetExpression(datePart);

    // prepare the sorter
    ISortClause datePartSortClause = new SortClause(datePartField, null, SortOperator.Descending);
    datePartSortClause.EmitAliasForExpressionAggregateField = true;
    ISortExpression sorter = new SortExpression(datePartSortClause);
    sorter.Add(OrdersFields.OrderDate | SortOperator.Descending);