Private Sub master_Page_PreLoad(sender As Object, e As System.EventArgs)
        If (Not IsPostBack) Then
            ' Impostare il token Anti-XSRF
            ViewState(AntiXsrfTokenKey) = Page.ViewStateUserKey
            ViewState(AntiXsrfUserNameKey) = If(Context.User.Identity.Name, String.Empty)
        Else
            ' Convalidare il token Anti-XSRF
            If (Not DirectCast(ViewState(AntiXsrfTokenKey), String) = _antiXsrfTokenValue _
                Or Not DirectCast(ViewState(AntiXsrfUserNameKey), String) = If(Context.User.Identity.Name, String.Empty)) Then
                Throw New InvalidOperationException("Convalida del token Anti-XSRF non riuscita.")
            End If
        End If
    End Sub