The way of getting Profile instance from a page context is Profile.GetProfile(). But how to do this when you need to get it from App_Code for instance. Here is the way:
MembershipUser mUser = Membership.GetUser(UserId);
ProfileCommon prof = (ProfileCommon)System.Web.Profile.ProfileBase.Create(mUser.UserName);
the object "prof" has all profile fields as in a page.