Integrating PayPal Payments （转）

http://www.west-wind.com/presentations/PayPalIntegration/PayPalIntegration.asp
By Rick Strahl

E-Commerce applications require mechanisms for payment. Although more commonly than not e-Commerce sites will use full credit card processing gateways, giving PayPal as an additional option of payment provides additional payment options for your customers, especially those that don’t want to pay by credit card over the Internet. If you run a Web shop that uses direct credit card processing and want to integrate PayPal seamlessly, you’ll find that using PayPal as a processing service is not as straight forward as using a payment gateway. In this article I describe how you can minimize the external PayPal interaction and work the PayPal payment into the order processing workflow to provide a seamless interface using ASP.NET and C#. However, the principles used here should be applicable to any Web programming environment.