public User AddInterest(int userId, string interestName) { User user = (User)_userRepo.Get(userId); Interest interest = _interestRepository.GetByName(interestName); if (user.Interests.Contains(interest)) { return(null); } if (interest == null) { Interest newInterest = new Interest { Name = interestName }; var saved = _interestRepository.Save(newInterest); saved.AddUser(user); _interestRepository.Update(saved); } else { interest.AddUser(user); _interestRepository.Update(interest); } return(user); }