c# - Paypal IPN リスナーが値を返さない

Question

C# MVC Web サイトで IPN リスナーを作成しようとしています。オンラインで調べた後、以下の ActionResult を作成できました。

リスナーは「VERIFIED」応答を受け取りますが、残念ながら支払いに関する他の情報を受け取っていないようです。

    [HttpPost]
    public ActionResult IPN()
    {
        var log = new LogMessage();
        log.LogMessageToFile("IPN recieved!");
        var formVals = new Dictionary<string, string>();
        formVals.Add("cmd", "_notify-validate");

        string response = GetPayPalResponse(formVals, true);

        if (response == "VERIFIED")
        {
            log.LogMessageToFile("IPN VERIFIED!");
            //validate the order
            string sAmountPaid = Request.QueryString["amt"];
            string sPayment = ConfigurationManager.AppSettings["amount"].ToString();
            Decimal amountPaid = 0;
            Decimal Payment = 0;
            Decimal.TryParse(sAmountPaid, out amountPaid);
            Decimal.TryParse(sPayment, out Payment);

            if (Payment <= amountPaid)
            {
                log.LogMessageToFile("IPN Correct amount");
                //process it
                try
                {
                    string GUID = Request.QueryString["cm"];
                    string strGatewayResponse = Request.QueryString["tx"];
                    var data = new Datalayer();
                    data.AddPayment(GUID, amountPaid, strGatewayResponse, true);
                    log.LogMessageToFile("IPN Commplete");
                    return Redirect("/Payment/Success");
                }
                catch
                {
                    log.LogMessageToFile("IPN Error");
                    return Redirect("/Payment/Error");
                }
            }
            else
            {
                log.LogMessageToFile("IPN Incorrect amount!");
                log.LogMessageToFile("IPN amount:" + Request.QueryString["payment_gross"]);
                log.LogMessageToFile("IPN GUID:" + Request.QueryString["custom"]);
                log.LogMessageToFile("IPN ID:" + Request.QueryString["txn_id"]);
                return Redirect("/Payment/Error");
            }
        }
        log.LogMessageToFile("IPN not verified!");
        return View("/Payment/Error");
    }


 string GetPayPalResponse(Dictionary<string, string> formVals, bool useSandbox)
    {

        string paypalUrl = useSandbox ? "https://www.sandbox.paypal.com/cgi-bin/webscr"
            : "https://www.paypal.com/cgi-bin/webscr";


        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(paypalUrl);

        // Set values for the request back
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";

        byte[] param = Request.BinaryRead(Request.ContentLength);
        string strRequest = Encoding.ASCII.GetString(param);



        StringBuilder sb = new StringBuilder();
        sb.Append(strRequest);

        foreach (string key in formVals.Keys)
        {
            sb.AppendFormat("&{0}={1}", key, formVals[key]);
        }
        strRequest += sb.ToString();
        req.ContentLength = strRequest.Length;

        string response = "";
        using (StreamWriter streamOut = new StreamWriter(req.GetRequestStream(), System.Text.Encoding.ASCII))
        {

            streamOut.Write(strRequest);
            streamOut.Close();
            using (StreamReader streamIn = new StreamReader(req.GetResponse().GetResponseStream()))
            {
                response = streamIn.ReadToEnd();
            }
        }

        return response;
    }

非常に単純なものが欠けている可能性が高いです。

どんな助けでも素晴らしいでしょう。