using.cs

        public RatingDTO GetUserRatingForWhiskey(Guid userId, Guid whiskeyId)
        {
            using(IUnitOfWork uow = _unitOfWorkFactory.Create("RatingService.GetUserRatingForWhiskey"))
            {
                User u = uow.UserRepository.FindById(userId);
                Whiskey w = uow.WhiskeyRepository.FindById(whiskeyId);

                if(u == null)
                {
                    throw new ArgumentException(string.Format("No User with id {0} exists.", userId));
                }

                if(w == null)
                {
                    throw new ArgumentException(string.Format("No Whiskey with id {0} exists.", whiskeyId));
                }

                return (from r in u.Ratings where r.ReviewOf.Id == whiskeyId select RatingDTO.Create(r)).FirstOrDefault();
            }
        }