/// <summary>
        /// Void an order
        /// </summary>
        /// <param name="orderGuid">Order guid</param>
        /// <returns></returns>
        public VoidTransactionResult VoidTransaction(String orderGuid)
        {
            var result = new VoidTransactionResult();

            var transx = _sagePayServerTransactionService.GetSagePayServerTransactionByVendorTxCode(orderGuid);

            if (transx == null)
            {
                result.Message = String.Format("SagePay Server vendor transaction code {0} does not exist.", orderGuid);
                return result;
            }

            var webClient = new WebClient();
            var voidGuid = Guid.NewGuid();

            var data = new QueryStringNameValueCollection
                           {
                               {"VPSProtocol", SagePayHelper.GetProtocol()},
                               {"TxType", "VOID"},
                               {"Vendor", _sagePayServerPaymentSettings.VendorName},
                               {"VendorTxCode", voidGuid.ToString()},
                               {"VPSTxId", transx.VpsTxId},
                               {"SecurityKey", transx.SecurityKey},
                               {"TxAuthNo", transx.TxAuthNo},
                           };

            var postUrl = SagePayHelper.GetSageSystemUrl(_sagePayServerPaymentSettings.ConnectTo, "void");

            string strResponse;

            try
            {

                var responseData = webClient.UploadValues(postUrl, data);

                strResponse = Encoding.ASCII.GetString(responseData);

            }
            catch (WebException ex)
            {
                result.Message = (String.Format(
                    @"Your server was unable to release this transaction with Sage Pay.
                    Check that you do not have a firewall restricting the POST and
                    that your server can correctly resolve the address {0}. <br/>
                    The Status Number is: {1}<br/>
                    The Description given is: {2}", postUrl, ex.Status, ex.Message));
                return result;
            }

            if (string.IsNullOrWhiteSpace(strResponse))
            {
                result.Message = (String.Format(
                    @"Your server was unable to register this transaction with Sage Pay.
                    Check that you do not have a firewall restricting the POST and
                    that your server can correctly resolve the address {0}.", postUrl));
                return result;
            }
            var strStatus = SagePayHelper.FindField("Status", strResponse);
            var strStatusDetail = SagePayHelper.FindField("StatusDetail", strResponse);

            switch (strStatus)
            {
                case "OK":

                    result.Success = true;
                    break;

                case "MALFORMED":
                    result.Message = (string.Format("Error ({0}: {1}) <br/> {2}", strStatus, strStatusDetail, data.Encode()));
                    break;

                case "INVALID":
                    result.Message = (string.Format("Error ({0}: {1}) <br/> {2}", strStatus, strStatusDetail, data.Encode()));
                    break;

                default:
                    result.Message = (string.Format("Error ({0}: {1})", strStatus, strStatusDetail));
                    break;

            }

            return result;
        }
        /// <summary>
        /// Register a new transaction with Sagepay before the iframe shows. In fact, this method should give us the URL for the iframe
        /// </summary>
        /// <returns></returns>
        public RegisterTransactionResult RegisterTransaction()
        {
            var result = new RegisterTransactionResult();

            if (_request.IsLocal)
            {
                result.Message =
                    "This plugin does not work in local hosts. You need to publish NopCommerce on a publicly accessible internet address.";
                return result;
            }

            var webClient = new WebClient();

            var orderGuid = Guid.NewGuid();

            var data = new QueryStringNameValueCollection
                           {
                               {"VPSProtocol", SagePayHelper.GetProtocol()},
                               {"TxType", TransactTypeValues.Deferred.ToString()},//we always use Deferred because we only take the payment after user has confirmed
                               {"Vendor", _sagePayServerPaymentSettings.VendorName.ToLower()},
                               {"VendorTxCode", orderGuid.ToString()}
                           };

            if (!String.IsNullOrWhiteSpace(_sagePayServerPaymentSettings.PartnerId))
                data.Add("ReferrerID", _sagePayServerPaymentSettings.PartnerId);

            var cart = _workContext.CurrentCustomer.ShoppingCartItems.ToList();
            cart = cart.Where(sci => sci.ShoppingCartType == ShoppingCartType.ShoppingCart).ToList();

            var orderTotal = _orderTotalCalculationService.GetShoppingCartTotal(cart).GetValueOrDefault();

            data.Add("Amount", orderTotal.ToString("F2", CultureInfo.InvariantCulture));

            data.Add("Currency", _workContext.WorkingCurrency != null
                         ? _workContext.WorkingCurrency.CurrencyCode
                         : _currencyService.GetCurrencyById(_currencySettings.PrimaryStoreCurrencyId).CurrencyCode);

            data.Add("Description", "eCommerce Order from " + _sagePayServerPaymentSettings.VendorName);

            // The Notification URL is the page to which Server calls back when a transaction completes
            data.Add("NotificationURL", _webHelper.GetStoreLocation() + "Plugins/PaymentSagePayServer/NotificationPage");

            // Billing Details
            data.Add("BillingSurname", _workContext.CurrentCustomer.BillingAddress.LastName);
            data.Add("BillingFirstnames", _workContext.CurrentCustomer.BillingAddress.FirstName);
            data.Add("BillingAddress1", _workContext.CurrentCustomer.BillingAddress.Address1);

            if (!String.IsNullOrWhiteSpace(_workContext.CurrentCustomer.BillingAddress.Address2))
                data.Add("BillingAddress2", _workContext.CurrentCustomer.BillingAddress.Address2);

            data.Add("BillingCity", _workContext.CurrentCustomer.BillingAddress.City);
            data.Add("BillingPostCode", _workContext.CurrentCustomer.BillingAddress.ZipPostalCode);
            data.Add("BillingCountry", _workContext.CurrentCustomer.BillingAddress.Country.TwoLetterIsoCode); //TODO: Verify if it is ISO 3166-1 country code

            if (_workContext.CurrentCustomer.BillingAddress.StateProvince != null && _workContext.CurrentCustomer.BillingAddress.Country.TwoLetterIsoCode.ToLower() == "us")
            {
                var state = _workContext.CurrentCustomer.BillingAddress.StateProvince.Abbreviation;
                data.Add("BillingState", (state.Length > 2) ? state.Substring(0, 2) : state);
            }

            if (!String.IsNullOrWhiteSpace(_workContext.CurrentCustomer.BillingAddress.PhoneNumber))
                data.Add("BillingPhone", _workContext.CurrentCustomer.BillingAddress.PhoneNumber);

            // Delivery Details
            if (_workContext.CurrentCustomer.ShippingAddress != null)
            {
                data.Add("DeliverySurname", _workContext.CurrentCustomer.ShippingAddress.LastName);
                data.Add("DeliveryFirstnames", _workContext.CurrentCustomer.ShippingAddress.FirstName);
                data.Add("DeliveryAddress1", _workContext.CurrentCustomer.ShippingAddress.Address1);

                if (!String.IsNullOrWhiteSpace(_workContext.CurrentCustomer.ShippingAddress.Address2))
                    data.Add("DeliveryAddress2", _workContext.CurrentCustomer.ShippingAddress.Address2);

                data.Add("DeliveryCity", _workContext.CurrentCustomer.ShippingAddress.City);
                data.Add("DeliveryPostCode", _workContext.CurrentCustomer.ShippingAddress.ZipPostalCode);

                if (_workContext.CurrentCustomer.ShippingAddress.Country != null)
                {
                    data.Add("DeliveryCountry", _workContext.CurrentCustomer.ShippingAddress.Country.TwoLetterIsoCode);

                    if (_workContext.CurrentCustomer.ShippingAddress.StateProvince != null && _workContext.CurrentCustomer.ShippingAddress.Country.TwoLetterIsoCode.ToLower() == "us")
                    {
                        var state = _workContext.CurrentCustomer.ShippingAddress.StateProvince.Abbreviation;
                        data.Add("DeliveryState", (state.Length > 2) ? state.Substring(0, 2) : state);
                    }
                }

                if (!String.IsNullOrWhiteSpace(_workContext.CurrentCustomer.ShippingAddress.PhoneNumber))
                    data.Add("DeliveryPhone", _workContext.CurrentCustomer.ShippingAddress.PhoneNumber);

            }
            else
            {
                data.Add("DeliverySurname", "");
                data.Add("DeliveryFirstnames", "");
                data.Add("DeliveryAddress1", "");
                data.Add("DeliveryAddress2", "");
                data.Add("DeliveryCity", "");
                data.Add("DeliveryPostCode", "");
                data.Add("DeliveryCountry", "");
                data.Add("DeliveryState", "");
                data.Add("DeliveryPhone", "");
            }

            data.Add("CustomerEMail", _workContext.CurrentCustomer.Email);

            //var strBasket = String.Empty;
            //strBasket = cart.Count + ":";

            //for (int i = 0; i < cart.Count; i++)
            //{
            //    ShoppingCartItem item = cart[i];
            //    strBasket += item.ProductVariant.FullProductName) + ":" +
            //                    item.Quantity + ":" + item.ProductVariant.Price + ":" +
            //                    item.ProductVariant.TaxCategoryId;
            //};

            //data.Add("Basket", strBasket);

            data.Add("AllowGiftAid", "0");

            // Allow fine control over AVS/CV2 checks and rules by changing this value. 0 is Default
            //data.Add("ApplyAVSCV2", "0");

            // Allow fine control over 3D-Secure checks and rules by changing this value. 0 is Default
            //data.Add("Apply3DSecure", "0");

            if (_sagePayServerPaymentSettings.Profile == ProfileValues.Low)
            {
                data.Add("Profile", "LOW"); //simpler payment page version.
            }

            var sageSystemUrl = SagePayHelper.GetSageSystemUrl(_sagePayServerPaymentSettings.ConnectTo, "purchase");

            string strResponse;

            try
            {

                var responseData = webClient.UploadValues(sageSystemUrl, data);

                strResponse = Encoding.ASCII.GetString(responseData);
            }
            catch (WebException ex)
            {

                result.Message= String.Format(@"Your server was unable to register this transaction with Sage Pay.
                    Check that you do not have a firewall restricting the POST and
                    that your server can correctly resolve the address {0}. <br/>
                    The Status Number is: {1}<br/>
                    The Description given is: {2}", sageSystemUrl, ex.Status, ex.Message);

                return result;

            }

            if (!string.IsNullOrWhiteSpace(strResponse))
            {

                var strStatus = SagePayHelper.FindField("Status", strResponse);
                var strStatusDetail = SagePayHelper.FindField("StatusDetail", strResponse);

                switch (strStatus)
                {
                    case "OK":

                        var strVpsTxId = SagePayHelper.FindField("VPSTxId", strResponse);
                        var strSecurityKey = SagePayHelper.FindField("SecurityKey", strResponse);
                        var strNextUrl = SagePayHelper.FindField("NextURL", strResponse);

                        var transx = new SagePayServerTransaction
                        {
                            CreatedOnUtc = DateTime.UtcNow,
                            VpsTxId = strVpsTxId,
                            SecurityKey = strSecurityKey,
                            NotificationResponse = strResponse.Replace(Environment.NewLine, ";"),
                            VendorTxCode = orderGuid.ToString(),
                        };

                        //Store this record in DB
                        _sagePayServerTransactionService.InsertSagePayServerTransaction(transx);

                        result.Success = true;
                        result.PaymentUrl = strNextUrl;

                        return result;

                    case "MALFORMED":

                        result.Message = string.Format("Error {0}, {1} - {2}", strStatus, strStatusDetail, data.Encode());

                        break;

                    case "INVALID":

                        result.Message = string.Format("Error {0}, {1} - {2}", strStatus, strStatusDetail, data.Encode());

                        break;

                    default:

                        result.Message = string.Format("Error {0}, {1}", strStatus, strStatusDetail);

                        break;
                }

            }

            return result;
        }