Asp.Net Mvc: Social Accounts Integration in existing application

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C#

ASP.NET

MVC

OWIN

I am working on some Asp.Net Mvc applications since last 4 years. I have used Entity Framework Code Fist approach in these application. So there are multiple databases which contains lot of tables.

Now I want to integrate social websites login and register. I have searched on it and I got two methods to implement it. First method my using custom code like facebook login etc and second method is here MVC 5 App with Facebook..

Second method looks pretty easy but there are lot of complex things in it. I am using custom User table and there is a different user registration process like

Register -> Email Verfication --> Admin approval

My Problem:

I can't modify my user table on this stage so What will be better way to accomplish it. I think above link demo will be better options of new web applications. Please share your experience regards this problem.

Thank you