I’ve been asked to integrate a windows form application with SagePay to take payments directly from the application. The SagePay documentation talks about ASP.NET so I’m not sur
I know some payment processors have a connection option where the payment part is hosted on a form on their server. You could try embedding a web browser control into your app to display the payment page.
Usually there is another type of connection option where you can send your information via HttpWebRequest, but I'm not sure that this would work as it requires SSL. Since you are running your app as a desktop client, I'm not sure what you would have available.