I am running an issue with google openid identifier. I am using dotnetopenauth library (successor of dotnetopenid) in simple asp.net mvc project. During tests on localhost
Google's openid is indeed per domain (hey, it bit the SO team, so you're in good company). It really comes down to the implementation details of each openid provider - google have gone a slightly different (but technically valid) route to most. For testing, you might try the blogger provider (still your google account) - it is a bit more static.
Google OP creates a unique and "anonymous"-looking Claimed Identifier for each user-RP Realm combination. (it is not based on the domain, but the full RP realm, or at least more of it than just the domain). Port number is part of the realm URI, so if your site on localhost changes port numbers occasionally as VS can do without warning, your claimed id will change. Also, if you set up your site to make your claimed_id an "admin" in development, it won't be the correct admin claimed_id in production since the realm will be different.