ASP.NET Web API social authentication for Web and Mobile

Question

My question is kind of complex so bear with me as I try to lay it out nicely what I am struggling with.

Goal

Have an ASP.NET website that lets u

Answer 1

You may want to have a look at this series of articles to see whether it covers your goal:

Token Based Authentication using ASP.NET Web API 2, Owin, and Identity by Taiseer Joudeh (who also frequently answers questions on SO)

The articles are about creating a token based authentication service using OWIN and one of the parts cover using external logins (such as Facebook and Google+). The examples are primarily centered around a web application as consumer of the web service, but it should work on mobile applications as well. The articles have a GitHub project associated and a very active comment section, where hardly any question goes unanswered.

Hope this may lead you to your goal.