I am adding a new area to an existing mvc 3 razor app as an admin area for managing some settings and content. The rest of the site is currently secured by a custom provider
There is actually very little headache involved.
Simply add all the MembershipProviders you want in web.config:
As you can see I have added two providers. I have also specified a default provider.
I can then switch between the two like this:
var membershipProvider1 = Membership.Providers["MembershipProvider1"];
membershipProvider1.ValidateUser("Mike", "banana");
var membershipProvider2 = Membership.Providers["MembershipProvider2"];
membershipProvider2.ValidateUser("Mike", "orange");
You probably want to wrap that into an application service or something, but you get the idea. Not so much headache, right?