My vb.net project includes a form with an Infragistics UltraGrid, in which one column, "Product_Code"` is a `DropDownList` style, populated by a ValueList.

What happens is, on the first row of the grid (Index 0), the item I select fills in the in the grid, and I can enter the rest of the data as I wish to.

However, when I add a second row (index 1 or higher), the ValueList remains the same, but whenever I click on a value, it inserts a `Null` or `Nothing` value into the "Product_Code" column. Is there anything alarmingly obvious which I'm doing wrong here?

I can't work out why this is happening

ugProducts.UpdateData()

For Each ugr In ugProducts.Rows
If ugr.Cells("Product_Code").Value = ugProducts.Rows(ugProducts.Rows.Count - 1).Cells("Product_Code").Value And ugr.Index <> ugProducts.Rows(ugProducts.Rows.Count - 1).Index Then
MsgBox("Cannot add the same product twice", MsgBoxStyle.OkOnly, "Error adding product")
ugProducts.Rows(ugProducts.Rows.Count - 1).Delete(False)
Exit Sub
End If
Next

Try
If supplier = "" Then
sql = "SELECT [Base_Code] FROM [Products]"
dtProducts = getDT(sql)

For Each dr In dtProducts.Rows
vlProducts.ValueListItems.Add(dr.Item("Base_Code"), dr.Item("Base_Code"))
Next
Else
Dim ProductsDt As New DataTable

Using ProductsDa = New OleDbDataAdapter("SELECT [Product_Code] FROM [Product Suppliers] WHERE Supplier_Code=?", con)
ProductsDa.SelectCommand.Parameters.Add("@suppliercode", OleDbType.VarChar).Value = supplier
ProductsDa.Fill(ProductsDt)
End Using

vlProducts.ValueListItems.Clear()

For Each dr In ProductsDt.Rows
vlProducts.ValueListItems.Add(dr.Item("Product_Code"), dr.Item("Product_Code"))
Next
ugProducts.DisplayLayout.Rows(0).Cells("Product_Code").ValueList = vlProducts
End If