Pay Multiple items at once using PayPal REST API ASP.NET MVC

Question

Hi i know this is a noob question but i cant find any documentation for this, I want to pay 1 or more items in the same transaction, but i get this error:

Exception in HttpConnection Execute: Invalid HTTP response The remote server returned an error: (400) Bad Request.

im hard-coding the item-list part, but i dont understan the differences beetween Amount.Total and the price of all my items price * quantity

public ActionResult CreatePayment(string description, decimal price, decimal tax = 0, decimal shipping = 0)
    {
        var viewData = new PayPalViewData();
        var guid = Guid.NewGuid().ToString();

        var paymentInit = new Payment
        {
            intent = "authorize",
            payer = new Payer
            {
                payment_method = "paypal"
            },
            transactions = new List<Transaction>
            {
                new Transaction 
                {
                    item_list = new ItemList{
                        items = new List<Item>{
                                new Item{
                                name = "item 1",
                                currency = "USD",
                                price = "20",
                                quantity = "2"
                                },
                                new Item{
                                name = "item 2",
                                currency = "USD",
                                price = "40",
                                quantity = "1"
                                },
                                new Item{
                                name = "item 3",
                                currency = "USD",
                                price = "40",
                                quantity = "1"
                                }
                        }
                    },
                    amount = new Amount
                    {
                        currency = "EUR",
                        total = (price + tax + shipping).ToString(),
                        details = new Details
                        {
                            subtotal = price.ToString(),
                            tax = tax.ToString(),
                            shipping = shipping.ToString()
                        }
                    },
                    description = description
                },
            },
            redirect_urls = new RedirectUrls
            {
                return_url = Utilities.ToAbsoluteUrl(HttpContext, String.Format("~/paypal/confirmed?id={0}", guid)),
                cancel_url = Utilities.ToAbsoluteUrl(HttpContext, String.Format("~/paypal/canceled?id={0}", guid)),
            },
        };

        viewData.JsonRequest = JObject.Parse(paymentInit.ConvertToJson()).ToString(Formatting.Indented);

        try
        {
            var accessToken = new OAuthTokenCredential(ConfigManager.Instance.GetProperties()["ClientID"], ConfigManager.Instance.GetProperties()["ClientSecret"]).GetAccessToken();
            var apiContext = new APIContext(accessToken);
            var createdPayment = paymentInit.Create(apiContext);

            var approvalUrl = createdPayment.links.ToArray().FirstOrDefault(f => f.rel.Contains("approval_url"));

            if (approvalUrl != null)
            {
                Session.Add(guid, createdPayment.id);

                return Redirect(approvalUrl.href);
            }

            viewData.JsonResponse = JObject.Parse(createdPayment.ConvertToJson()).ToString(Formatting.Indented);

            return View("Error", viewData);
        }
        catch (PayPalException ex)
        {
            viewData.ErrorMessage = ex.Message;

            return View("Error", viewData);
        }
    }

if i delete the item-list, it works but just 1 item described in the amount what can i do? do you have a guide for this? Paypal guids and demos are for one item only

Thanks

Answer 1

My guess, which is without seeing the full response is that your total does not add up with the details/item list. The validation adds up all the item values, which has to equal subtotal, the subtotal + tax etc (details) has to equal total.

sum (item.price * item.count) == sub total

sum of details == total