Private Sub zippa(ByVal sender As System.Object, ByVal e As System.EventArgs)

        Dim DaComprimere As String = Server.MapPath("file.htm")
        Dim Archivio As String = Server.MapPath("file.rar")

        Using streamWriter As New FileStream(DaComprimere, FileMode.Create, FileAccess.Write, FileShare.None)
            Using streamReader As New FileStream(Archivio, FileMode.Open, FileAccess.Read, FileShare.Read)
                Using gzip As New GZipStream(streamWriter, CompressionMode.Compress, True)
                    Dim buffer As Byte() = New Byte(streamReader.Length - 1) {}
                    streamReader.Read(buffer, 0, buffer.Length)
                    gzip.Write(buffer, 0, buffer.Length)
                End Using
            End Using
        End Using
    End Sub