how to add blank row in multicolumncombobox windows

HI

I want to show blank row at top of multicolumncombobox. My code is in vb.net

   Dim dr = dbManager.GetDataReader("SP_NewLotNo_Select", CommandType.StoredProcedure, parameters.ToArray(), connection)
        Dim dt As DataTable = New DataTable()

        dt.Load(dr)

        Try
            'Insert the Default Item to DataTable.
            Dim row As DataRow = dt.NewRow()
            row(0) = 0
            row(1) = "---Select---"
            dt.Rows.InsertAt(row, 0)

            'Assign DataTable as DataSource.
            cmbLotNo.DataSource = dt
            cmbLotNo.DisplayMember = "LotNumber"
            cmbLotNo.ValueMember = "NewLotId"

            cmbLotNo.Refresh()

            cmbLotNo.SelectedIndex = -1

            cmbLotNo.AutoCompleteMode = AutoCompleteMode.SuggestAppend
            cmbLotNo.AutoSizeDropDownToBestFit = False
            cmbLotNo.BestFitColumns(True, False)
            cmbLotNo.Columns(0).IsVisible = False
            cmbLotNo.Columns(3).TextAlignment = ContentAlignment.MiddleRight
            Me.cmbLotNo.AutoSizeDropDownToBestFit = True

            Me.cmbLotNo.AutoFilter = True
            Me.cmbLotNo.DisplayMember = "LotNumber"
            Dim filter As New FilterDescriptor()
            filter.PropertyName = Me.cmbLotNo.DisplayMember
            filter.Operator = FilterOperator.Contains
            Me.cmbLotNo.EditorControl.MasterTemplate.FilterDescriptors.Add(filter)
        Catch ex As Exception
            MessageBox.Show("Error:- " & ex.Message)
        Finally
            dr.Close()
            dbManager.CloseConnection(connection)
        End Try

its working but not perfectly as i want attaching image for output.

Thanks

Nandan