ASP.NET MVC 4 web application allows users to log in from an external provider, such as Facebook, Twitter, Microsoft or Google and then integrate into your web application. Some OAuth/OpenId providers like Facebook, Google allow to access email. This article explains how to save the email in your database.
Before implementing, first lets consider following points:
1. User name is different from Email.
2. Email might be different for different providers.
3. Email is optional(some external provider like twitter doesn’t allow to access email).