Using AMO to design UBO aggregates run into an error

Hi.

I try to use used based optimization with the following AMO code. But I get an error, that an attribute of a dimension is NULL and the AggregationDesigner cannot build an aggregate on this. Is this a problem in the code (like a problem with the query list (I do put the "Dataset" column into it only actually. ). - If I try to build an aggregate with the wizard in SSDT everything is fine.

Cheers,

Nils

    Dim strSQL As String = "SELECT [Dataset],COUNT(*) FROM [dbo].[OlapQueryLog] WHERE MSOLAP_ObjectPath = @ObjPath AND StartTime >= @StartTime GROUP BY [Dataset]"
            Dim SqlComm As SqlCommand = New SqlCommand(strSQL, _SqlConn)
            SqlComm.Parameters.Add(StartTime)
            SqlComm.Parameters.Add(ObjPath)
            Dim SqlReader As SqlDataReader = SqlComm.ExecuteReader

            Dim FirstTime As Boolean = True
            Dim Finished As Boolean = False
            Dim Optimization As Double
            Dim Storage As Double
            Dim AggregationCount As Int64

            If SqlReader.HasRows Then
                While SqlReader.Read
                    QueryList.Add(SqlReader.GetString(0)) 'SqlReader.GetInt32(1).ToString + "," +
                End While

                With AggrDesign
                    .InitializeDesign()
                    While Not Finished And Optimization < MaxOptimization And Storage < MaxStorage And AggregationCount < MaxAggregationCount
                        If FirstTime Then
                            .DesignAggregations(Optimization, Storage, AggregationCount, Finished, QueryList)
                            FirstTime = False
                        Else
                            .DesignAggregations(Optimization, Storage, AggregationCount, Finished)
                        End If
                    End While                    
                    .FinalizeDesign()
                    .Update()
                End With
            End If