public double CalculateOrderNetAmount(Order order)
        {
            double netAmount = 0;

            var p = from book in order.Books
                    group book by new { book.ID, book.Price } into g
                    select new Book { ID = g.Key.ID, Price = g.Key.Price };

            netAmount += CalculateDiscount(p.ToList());

            return netAmount;
        }
 public ShoppingCartServiceTests()
 {
     customer = new Customer {ID=1234, Name = "Matt" };
     order = new Order();
     order.Customer = customer;
 }