How to create and execute payment gateway with security?MVC

http://ravi-kumar-singh.blogspot.in/2014/07/how-to-integrate-paypal-in-aspnet-mvc-5.html

https://gist.github.com/samnaseri/2211309

https://www.codeproject.com/Articles/870870/Using-Paypal-Rest-API-with-ASP-NET-MVC

https://github.com/paypal/PayPal-NET-SDK

https://docs.microsoft.com/en-us/aspnet/web-forms/overview/getting-started/getting-started-with-aspnet-45-web-forms/checkout-and-payment-with-paypal

https://forums.asp.net/t/1963568.aspx?how+to+integrate+payment+gateway+system+in+c+net+without+using+PayPal+Gateway+