public bool DoCheckoutPayment(string finalPaymentAmount, string token, string PayerID, ref NVPCodec decoder, ref string retMsg)
        {
            if (bSandbox)
            {
                pEndPointURL = pEndPointURL_SB;
            }

            NVPCodec encoder = new NVPCodec();
            encoder["METHOD"] = "DoExpressCheckoutPayment";
            encoder["TOKEN"] = token;
            encoder["PAYERID"] = PayerID;
            encoder["PAYMENTREQUEST_0_AMT"] = finalPaymentAmount;
            encoder["PAYMENTREQUEST_0_CURRENCYCODE"] = "EUR";
            encoder["PAYMENTREQUEST_0_PAYMENTACTION"] = "Sale";

            string pStrrequestforNvp = encoder.Encode();
            string pStresponsenvp = HttpCall(pStrrequestforNvp);

            decoder = new NVPCodec();
            decoder.Decode(pStresponsenvp);

            string strAck = decoder["ACK"].ToLower();
            if (strAck != null && (strAck == "success" || strAck == "successwithwarning"))
            {
                return true;
            }
            else
            {
                retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" +
                    "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" +
                    "Desc2=" + decoder["L_LONGMESSAGE0"];

                return false;
            }
        }
        public bool ShortcutExpressCheckout(Cart cart, string amt, ref string token, ref string retMsg)
        {
            int i;

            if (bSandbox)
            {
                pEndPointURL = pEndPointURL_SB;
                host = host_SB;
            }

            NVPCodec encoder = new NVPCodec();
            encoder["METHOD"] = "SetExpressCheckout";
            encoder["RETURNURL"] = returnURL;
            encoder["CANCELURL"] = cancelURL;
            encoder["BRANDNAME"] = "NCIRL Web Store";
            encoder["PAYMENTREQUEST_0_AMT"] = amt;
            encoder["PAYMENTREQUEST_0_ITEMAMT"] = amt;
            encoder["PAYMENTREQUEST_0_PAYMENTACTION"] = "Sale";
            encoder["PAYMENTREQUEST_0_CURRENCYCODE"] = "EUR";

            i = 0;
            foreach (var line in cart.Lines)
            {
                encoder["L_PAYMENTREQUEST_0_NAME" + i] = line.Product.Name.ToString();
                encoder["L_PAYMENTREQUEST_0_AMT" + i] = line.Product.Price.ToString();
                encoder["L_PAYMENTREQUEST_0_QTY" + i] = line.Quantity.ToString();
                i++;
            }

            string pStrrequestforNvp = encoder.Encode();
            string pStresponsenvp = HttpCall(pStrrequestforNvp);

            NVPCodec decoder = new NVPCodec();
            decoder.Decode(pStresponsenvp);

            string strAck = decoder["ACK"].ToLower();
            if (strAck != null && (strAck == "success" || strAck == "successwithwarning"))
            {
                token = decoder["TOKEN"];
                string ECURL = "https://" + host + "/cgi-bin/webscr?cmd=_express-checkout" + "&token=" + token;
                retMsg = ECURL;
                return true;
            }
            else
            {
                retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" +
                    "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" +
                    "Desc2=" + decoder["L_LONGMESSAGE0"];
                return false;
            }
        }
        public bool GetCheckoutDetails(string token, ref string PayerID, ref NVPCodec decoder, ref string retMsg)
        {
            if (bSandbox)
            {
                pEndPointURL = pEndPointURL_SB;
            }

            NVPCodec encoder = new NVPCodec();
            encoder["METHOD"] = "GetExpressCheckoutDetails";
            encoder["TOKEN"] = token;

            string pStrrequestforNvp = encoder.Encode();
            string pStresponsenvp = HttpCall(pStrrequestforNvp);

            decoder = new NVPCodec();
            decoder.Decode(pStresponsenvp);

            string strAck = decoder["ACK"].ToLower();
            if (strAck != null && (strAck == "success" || strAck == "successwithwarning"))
            {
                PayerID = decoder["PAYERID"];
                return true;
            }
            else
            {
                retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" +
                    "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" +
                    "Desc2=" + decoder["L_LONGMESSAGE0"];

                return false;
            }
        }