private Reservation ReadReservation(SqlDataReader reader)
        {
            int id         = (int)reader["Id"];
            int customerId = (int)reader["CustomerId"];
            int bookId     = (int)reader["BookId"];

            CustomerDAO customerDAO = new CustomerDAO();
            Customer    customer    = customerDAO.GetById(customerId);
            BookDAO     bookDAO     = new BookDAO();
            Book        book        = bookDAO.GetById(bookId);

            return(new Reservation(id, customer, book));
        }