public static class MyGlobalVariables
    {
        public static int TokenChoice
        {
            get
            {
                if (System.Web.HttpContext.Current.Session["TokenChoice"] == null)
                {
                    return -1;
                }
                else
                {
                    return (int)System.Web.HttpContext.Current.Session["TokenChoice"];
                }
            }
            set
            {
                System.Web.HttpContext.Current.Session["TokenChoice"] = value;
            }
        }
        public static int PaymentChoice
        {
            get
            {
                if (System.Web.HttpContext.Current.Session["PaymentChoice"] == null)
                {
                    return -1;
                }
                else
                {
                    return (int)System.Web.HttpContext.Current.Session["PaymentChoice"];
                }
            }
            set
            {
                System.Web.HttpContext.Current.Session["PaymentChoice"] = value;
            }
        }
        public static string CurrentUser
        {
            get
            {
                System.Web.HttpContext.Current.Session["CurrentUser"] = System.Web.HttpContext.Current.User.Identity.Name;
                return (string)System.Web.HttpContext.Current.Session["CurrentUser"];
            }
        }

    }

public ActionResult Payment(int tokenChoice, int paymentChoice)
    {
        ViewData["_CurrentUser"] =
            System.Web.HttpContext.Current.Session["_CurrentUser"] = User.Identity.Name;
        ViewBag.Payment = paymentChoice;
        MyGlobalVariables.PaymentChoice = paymentChoice;
        MyGlobalVariables.TokenChoice = tokenChoice;

        return View();
    }

[HttpPost]
    public ActionResult Payment()
    {
        NameValueCollection nvc = Request.Form;

        Trace.WriteLine("Http_Hmac: " + HTTP_HMAC);
        Trace.WriteLine("ipn_mode: " + nvc["ipn_mode"]);
        Trace.WriteLine("currency1: " + nvc["currency1"]);
       Trace.WriteLine("txn id: " + nvc["txn_id"]);
        var merchant_id = "9750af22c5fb6321c05fb0b4befb9ac1";
            var ipn_secret = "xxkuki1212xx";
        var order_total = MyGlobalVariables.PaymentChoice;

            if (String.IsNullOrEmpty(nvc["ipn_mode"]) || nvc["ipn_mode"] != "hmac")
            {
                Trace.WriteLine("IPN Mode is not HMAC");
                return View();
            }

            if (String.IsNullOrEmpty(HTTP_HMAC))
            {
                Trace.WriteLine("No HMAC signature sent");
                return View();
            }

            if (String.IsNullOrEmpty(nvc["merchant"]) || nvc["merchant"] != merchant_id.Trim())
            {
                Trace.WriteLine("No or incorrect Merchant ID passed");
                return View();
            }

            //var hmac = hash_hmac("sha512", request, ipn_secret.Trim());

            var txn_id = nvc["txn_id"];
            var item_name = nvc["item_name"];
            var item_number = nvc["item_number"];
            var amount1 = nvc["amount1"];
            var amount2 = float.Parse(nvc["amount2"], CultureInfo.InvariantCulture.NumberFormat);
            var currency1 = nvc["currency1"];
            var currency2 = nvc["currency2"];
            var status = Convert.ToInt32(nvc["status"]);
            var status_text = nvc["status_text"];
            Trace.WriteLine(status);
            if (currency1 != "USD") {
                Trace.WriteLine("Original currency mismatch!");
                return View();
            }

        if (Convert.ToInt32(amount1) < Convert.ToInt32(order_total))
        {
            Trace.WriteLine("Amount is less than order total!");
            return View();
        }

        if (status >= 100 || status == 2) {

                using (MyDatabaseEntities1 dc = new MyDatabaseEntities1())
                {
                var account = dc.Users.Where(a => a.Username == MyGlobalVariables.CurrentUser).FirstOrDefault();
                if (account != null && account.Paid == 0)
                {
                    Trace.WriteLine("Payment Completed");
                    Trace.WriteLine("Tokens to add: " + MyGlobalVariables.TokenChoice);
                    account.Tokens += MyGlobalVariables.TokenChoice;
                    account.Paid = 1;
                    dc.Configuration.ValidateOnSaveEnabled = false;
                    dc.SaveChanges();
                }
                }
              } else if (status < 0)
            {
                Trace.WriteLine(
                    "payment error, this is usually final but payments will sometimes be reopened if there was no exchange rate conversion or with seller consent");
            } else {
            using (MyDatabaseEntities1 dc = new MyDatabaseEntities1())
            {
                var account = dc.Users.Where(a => a.Username == MyGlobalVariables.CurrentUser).FirstOrDefault();
                if (account != null)
                {
                    account.Paid = 0;
                    dc.Configuration.ValidateOnSaveEnabled = false;
                    dc.SaveChanges();
                }
            }
            Trace.WriteLine("Payment is pending");
            }

        return View();
    }