protected void btnAddBook_Click(object sender, EventArgs e)
        {
            LibraryService service = ServiceFactory.CreateLibraryService();
            AddBookRequest request = new AddBookRequest();
            request.ISBN = ddlBookTitles.SelectedValue;

            service.AddBook(request);
            DisplayBooks();
        }
        public AddBookResponse AddBook(AddBookRequest request)
        {
            AddBookResponse response = new AddBookResponse();

            BookTitle bookTitle = _bookTitleRepository.FindBy( request.ISBN); 
            Book book = new Book();
            book.Title = bookTitle;
            book.Id = Guid.NewGuid();
            _bookRepository.Add(book);
            _uow.Commit();

            response.Success = true;

            return response;
        }