Question

what this method will return when the db is null for some reason? compile is fine and there is no return statement outside the using block.

public Guid GetUserId(string username)
    {

        using (AndeDBEntities db = new AndeDBEntities())
        {
            var userId =
                from u in db.Users
                where u.Username == username
                   && u.Deleted != true
                select new { UserID = u.UserId };
            if (userId == null || userId.Count() == 0) 
                return Guid.Empty;
            else 
                return userId.First().UserID;
        }
    }

Answer 1

If the db is null for some reason, this will likely raise an Exception at runtime. This will most likely be a NullReferenceException, but could be some other exception depending on how it was written.

However, this really shouldn’t be possible. db should always be valid, although db.Users may be null if the constructor (AndeDBEntities) doesn’t set it properly. In this case, you’ll get a NullReferenceException when you hit your LINQ query (ie: accessing db.Users).