Get Value of Dropdownlist with Filenames

I have this page to update products stored in a database. Everything works fine except for getting the SelectedValue of the DropDownList. The values (and text) of the DropDownList are taken from from the files in a directory. It should be a real easy one, but I can't figure it out. Here's my code:

 Imports System.IO
Imports System.Data

Partial Class Admin_Cms_edit_Products
Inherits System.Web.UI.Page

Dim productsLogic As New ProductsBLL

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
pnlEditor.Visible = False
End Sub

Protected Sub ...