codice:
    Private Sub scarica_mp3()
        'Download stringa rtf

        Dim messaggioErrore As String = ""
        Dim filePath As String = Me.Server.MapPath("Track01.mp3")

        Dim fi As FileInfo = New FileInfo(filePath)
        If Not fi.Exists Then
            messaggioErrore = "file non esistente"
        End If

        
        If messaggioErrore = "" Then
            ' imposta le headers 
            Response.Clear()
            Response.AddHeader("Content-Disposition", "attachment; filename=""" & fi.Name & """")
            Response.AddHeader("Content-Length", fi.Length.ToString())
            Response.ContentType = "application/octet-stream"

            ' leggo dal file e scrivo nello stream di risposta 
            Response.WriteFile(filePath)
            Response.End()

        Else
            Response.Write(String.Format("<script>alert(""{0}"");</script>", libreria.toStringaJS(messaggioErrore)))
            Response.Flush()
            Response.End()

        End If

    End Sub