how to get userid in membership?

i know how to get userid for a current user

 MembershipUser currentUser = Membership.GetUser();
 Guid currentUserId = (Guid)currentUser.ProviderUserKey;

But for my application i need to get userid of user who开发者_如何转开发 are not loginned in also. Because i need to assign the userid to different table which i m using.

Thank you in Advance

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Use the Membership.GetUser(username, userIsOnline) method, passing false as the userIsOnline parameter.