BP search query gets Valid Value error

Question

I am using the tutorial example to add all business partners to a combo box. The only change is to the query used:
RS.DoQuery("SELECT DISTINCT CardCode, CardName FROM OINV T0 join INV1 T1 on T0.DocEntry = T1.DocEntry WHERE U_Active = 'Y' ORDER BY CardName")
In this case, U_Active is a udf on the invoice detail level. When run, SAP returns an error Valid Value Already Exists. The combo box only displays the first two lines of data.
This query works perfectly as a query in SAP's Query Manager, returning exactly the expected data. there are no duplicates in the results.
The standard unedited tutorial example works also.
Any help or suggestions are much appreciated.

Answer 1

Code used:
   Private Sub AddBPCodeCombo(ByVal oCombo As SAPbouiCOM.ComboBox)
        Dim RS As SAPbobsCOM.Recordset
        Dim Bob As SAPbobsCOM.SBObob
        'Dim sSQL As String
        Try
            RS = oCompany.GetBusinessObject(SAPbobsCOM.BoObjectTypes.BoRecordset)
            RS.DoQuery("SELECT DISTINCT CardCode, CardName FROM OINV T0 join INV1 T1 on T0.DocEntry = T1.DocEntry WHERE U_Active = 'Y' ORDER BY CardName")
            RS.MoveFirst()
            While RS.EoF = False
                oCombo.ValidValues.Add(RS.Fields.Item("CardCode").Value, RS.Fields.Item("CardName").Value)
                RS.MoveNext()
            End While
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try
    End Sub