title: How to allow multiple authentication methods in ASP.NET?
body: <p>I'm building a new ASP.NET MVC application (in C#) and one of the requirements is to create a new database of members. For this, we'd need roles to manage the different types of members and profiles to manage the additional metadata attached to each member. So far so good, just use the standard MembershipProvider, RoleProvider and ProfileProvider provided as part of the .NET Framework.</p>
  
  <p>However, the catch is that I'd like to allow different authentication methods. I'd like Accounts and Login Credentials to have a one-to-many relationship (one account can have a number of login credentials attached). A user for example, might have both an OpenID and ActiveDirectory account attached to their account.</p>
  
  <p>However, after experimenting with a few ways we opted for the MembershipProvider route (explained how it was achieved as an answer below). </p>
  
  <p>My question is, how have people done this before and how would people suggest I approach it? It appears to be something that is achieved on quite a number of sites, yet a search on here doesn't return anything solid to play around with.</p>
  
  <p>EDIT: After looking around for a good period of hours overnight and this morning - I'm still not convincinced that butchering a single MembershipProvider would have been the easiest option. Does having multiple MembershipProviders give the same effect?</p>
  
  <p>BOUNTY EDIT: With no responses, I am assuming that there is no more optimal solution that the one I posted as an answer. Is this really the case? I'm offering a bounty to try and see if anyone has any further thoughts on this and whether there are better alternatives.</p>
  
  <p>BOUNTY ACCEPT EDIT: I think that WIF is the answer as accepted below, for a .NET 4 release and maybe other versions as it probably works with 3.5. Other than that, maybe a butchered MembershipProvider or adapted one may still be relevant.</p>