How to do login to my asp.net app using Facebook (or other ID)?

Question

How do sites like SO allow you to authenticate yourself via Facebook, OpenID, Google, Blogger, Twitter, etc?

I'm writing an ASP.NET (C#) site, and I'd like to be able to accept logins like this, in addition to offering the regular plain vanilla username/password that any other site has.

Where do I start?

Answer 1

You might want to try DotNetOpenAuth

Here's a similar question on SO with some more links

Answer 2

I would suggest you look at http://www.dotnetopenauth.net/

I believe SO may actually use this library - they definitely donated to the project this year (see https://blog.stackoverflow.com/2010/12/stack-overflow-gives-back-2010/).