public void Add(CourtBook book)
        {
            if (book.Client.Id == 0)
            {
                _clientService.Add(book.Client);
            }

            var courtBookEntity = new CourtBookEntity
            {
                CourtId = book.Court.Id,
                StartTime = book.StartTime,
                EndTime = book.EndTime,
                Price = book.Price,
                ReserveRequired = book.ReserveRequired,
                Reserve = book.Reserve,
                Paid = book.Paid,
                ClientId = book.Client.Id,
                Comment = book.Comment,
                UserId = book.User,
            };

            _context.CourtBooks.AddObject(courtBookEntity);
            _context.SaveChanges();

            book.Id = courtBookEntity.Id;
        }
        public void Update(CourtBook book)
        {
            if (book.Client.Id == 0)
            {
                _clientService.Add(book.Client);
            }

            var courtBookEntity = _context.CourtBooks.First(cb => cb.Id == book.Id);

            courtBookEntity = new CourtBookEntity
            {
                Id = book.Id,
                CourtId = book.Court.Id,
                StartTime = book.StartTime,
                EndTime = book.EndTime,
                Price = book.Price,
                ReserveRequired = book.ReserveRequired,
                Reserve = book.Reserve,
                Paid = book.Paid,
                ClientId = book.Client.Id,
                Comment = book.Comment,
                UserId = book.User,
            };

            _context.SaveChanges();
        }