Using Paypal Rest API with ASP.NET MVC 4

This is my first ever article on CodeProject and it's about the use of Paypal REST API for payments. It's a world of eCommerce now and everyone wants to integrate Paypal in their website for accepting payments online for either their services of products they are selling. So, this article is about the Integration of PAYPAL REST API in an ASP.NET MVC 4 Framework. I am using this framework because it is a quick way to start on any good web application. I have commented my code as much as possible, so that you can understand what actually is happening in the code. Still if you are not able to understand, then you can ask me. I won't hesitate to help, if I am available.