public Message Save(Book newBook)
        {
            Message message = new Message();
            string isbn = newBook.ISBN.Trim();
            if (isbn.Length != 13)
            {
                message.Status = "warning";
                message.Details = "ISBN Number must be thirteen (13) characters long.";
                return message;
            }
            bool isBookExixts = IsBookExists(newBook);

            if (isBookExixts)
            {
                message.Status = "error";
                message.Details = "ISBN Number is already exists.";
                return message;
            }

            try
            {
                aBookGateway.AddBook(newBook);
                message.Status = "success";
                message.Details = "Book Added Successfully";
            }
            catch (SqlException ex)
            {
                message.Status = "error";
                message.Details = ex.Message;
            }

            return message;
        }
        protected void saveButton_Click(object sender, EventArgs e)
        {
            string isbn = isbnTextBox.Text;
            string name = nameTextBox.Text;
            string author = authorTextBox.Text;

            Message message = new Message();

            Book aBook = new Book(isbn, name, author);
            message = aBookManager.Save(aBook);

            messageLabel.CssClass = message.Status;
            messageLabel.Text = message.Details;

            if (message.Status == "success")
            {
                ClearTextFields();
            }
        }