I’ve a site with user registration (ASP.Net Membership) and Facebook login button.
I use SetAuthCookie(model.UserName... in both login acions and everithing seems to work!
Now… what if a FB username is the same of already registered user?
Is there a best practice?
For my site, when there is a conflict between existing username and upcoming user’s facebook username, in that case at final stage of registration we ask to just enter username and then continue to application.