I have 2 DNN sites. I need to synchronize user table while registering user in one. ie. if a user register at site 1, that user will be available in site 2. So I need to use the query behind
UserController.CreateUser(userInfo).
You have to create entries in UserProtal table, so for example, you have two portals with id 0 and 1. If user registers to portal 0, UserController.CreateUser will create entry in UserPortal table with portal 0 and new userid. Once user is created, you have to create same kind of entry for portal 1 and new userid in same table.
Let me know if you have any other question on this