Visual Basic 2010 express Cargar directorio en listbox

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ListBox1.Items.Clear() 'borramos el listbox
        'especificamos carpeta y que buscar
        Dim fileNames = My.Computer.FileSystem.GetFiles(
            "c:\", FileIO.SearchOption.SearchTopLevelOnly, TextBox1.Text)
        

          For Each fileName As String In fileNames 'recorremos el directorio
          ListBox1.Items.Add(fileName) 'escribimos encontrado
          Next
    End Sub
End Class