Facebook API, Using FB Connect on email address

ASP.Net C# and FaceBook Connect.

I'm using Facebook connect on my site. If a new user connects through FB i create an account for them and all is fine. Wh开发者_如何学Pythonat i would also like to do is check to see if they already have a registered account.

So if someone connects that has not logged in but has an account i would like to be able to locate the account in my application a link it. I hoping this could be done via the email address?

Any ideas

Thanks

Richard

UPDATE: You need Connect.registerUsers:

This method is used to create an association between an existing user account on your site and that user's Facebook account, provided the user has not connected accounts before.

This method takes an array of account data, including a required email_hash and optional account data. For each connected account, if the user exists, the information is added to the set of the user's connected accounts. If the user has already authorized the site, the connected account is added in the confirmed state. If the user has not yet authorized the site, the connected account is added in the pending state.

If the user deactivates their external user account, then call connect.unregisterUsers. To get the number of friends a user has in the pending state, use connect.getUnconnectedFriendsCount.

If that doesn't resolve your question, this question is not a duplicate of yours, but the answers might give you a way forward:

• How do we register users — Facebook Connect users logging in the first time — when we cannot get an email address from facebook?