inoltre non riesco a far funzionare il tasto sfoglia

codice:
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim aaa As New OpenFileDialog()
        aaa.InitialDirectory = "c:\"
        aaa.Filter = "*.zip"
        If aaa.ShowDialog = DialogResult.OK Then
            selezionato.Text = aaa.OpenFile()
        End If
    End Sub