comOrders.CommandText = @"SELECT
                                    Products.ProductID,
                                    Products.Productname,
                                    [Order Details].Quantity,
                                    CAST([Order Details].UnitPrice as DECIMAL(5,2)) as Stuksprijs,
                                    CAST([Order Details].Quantity*[Order Details].UnitPrice as DECIMAL(10,2)) as Regeltotaal


                                    FROM Orders, [Order Details], Products
                                    WHERE Orders.OrderID=[Order Details].OrderID
                                    AND Products.ProductID=[Order Details].ProductID
                                    AND Orders.CustomerID=@klantID";

            comOrders.Parameters.Add("@klantID", SqlDbType.NChar);
            comOrders.Parameters["@klantID"].Value = ddKlantenIDs.Text;

            daKlanten.SelectCommand = comOrders;
            daKlanten.Fill(dsKlanten.Tables["orders"]);

            gvKlanten.DataSource = dsKlanten.Tables["orders"];
            gvKlanten.DataBind();