Paypal REST API - Passing parameter during the payment process - asp.net-mvc

Question

I am integrating Paypal direct payment into my ASP.NET MVC 5 project, by using Paypal's .NET SDK. Below are the steps:
I call PayPal.Api.Payment.Create(APIContext) to redirect to Paypal site, with a successful url;
In the callback action which corresponds to the successful url, call PayPal.Api.Payment.Execute(APIContext, ExecutionContext).
What I need is pass the new order's id to Paypal when calling Payment.Create(), and receive its value in Payment.Execute(), so it can know with which order the payment is associated.
Is it possible? Thanks a lot.

Answer 1

Based on the SDK and the API help pages, I would leverage off of the invoice_number property in the Transaction that you are sending to the Payments.Create() end point. This transaction will be part of the Response back from PayPal, meaning you can get the OrderNumber (now called invoice_number) back from the API.
Locate this line below: invoice_number = YOUR_ORDER_NUMBER
Your PayPal Request: (taken from SDK Samples)
var apiContext = Configuration.GetAPIContext();
// A transaction defines the contract of a payment - what is the payment for and who is fulfilling it.
var transaction = new Transaction()
{
amount = new Amount(){...},
description = "This is the payment transaction description.",
item_list = new ItemList(){...},
//SET YOUR ORDER NUMBER HERE
invoice_number = YOUR_ORDER_NUMBER
};
// A resource representing a Payer that funds a payment.
var payer = new Payer(){...};
// A Payment resource; create one using the above types and intent as `sale` or `authorize`
var payment = new Payment()
{
intent = "sale",
payer = payer,
transactions = new List<Transaction>() { transaction }
};
this.flow.AddNewRequest("Create credit card payment", payment);
// Create a payment using a valid APIContext
var createdPayment = payment.Create(apiContext);
The response from PayPal (Taken From Here):