Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        ListBox1.Items.Clear()

        Dim dir As New IO.DirectoryInfo(TextBox1.Text)

        Dim fname As IO.FileInfo

        Dim fname2 As IO.DirectoryInfo

        For Each fname In dir.GetFiles()

            ListBox1.Items.Add(fname)

        Next

        For Each fname2 In dir.GetDirectories()

            ListBox1.Items.Add(fname2)

        Next

    End Sub

End Class