static void Main(string[] args) { try { OrderItem apple = new OrderItem(1, "apple", 10.0, 80); OrderItem egg = new OrderItem(2, "eggs", 1.2, 200); OrderItem milk = new OrderItem(3, "milk", 50, 10); Order order1 = new Order(1, "Customer1", new List <OrderItem> { apple, egg, milk }); Order order2 = new Order(2, "Customer2", new List <OrderItem> { egg, milk }); Order order3 = new Order(3, "Customer2", new List <OrderItem> { apple, milk }); OrderService os = new OrderService(); os.AddOrder(order1); os.AddOrder(order2); os.AddOrder(order3); Console.WriteLine("GetAllOrders"); List <Order> orders = os.orders; orders.ForEach(o => Console.WriteLine(o)); Console.WriteLine(""); os.Sort((o1, o2) => o1.TotalPrice.CompareTo(o2.TotalPrice)); Console.WriteLine("GetAllOrders After sort"); orders = os.orders; orders.ForEach(o => Console.WriteLine(o)); Console.WriteLine(""); Console.WriteLine("GetOrdersByCustomerName:'Customer2'"); orders = os.QuaryByCustomer("Customer2"); orders.ForEach(o => Console.WriteLine(o)); Console.WriteLine(""); Console.WriteLine("GetOrdersByGoodsName:'apple'"); orders = os.QuaryByName("apple"); orders.ForEach(o => Console.WriteLine(o)); Console.WriteLine(""); Console.WriteLine("Remove order(id=2) and qurey all"); os.ReMove(2); orders.ForEach(o => Console.WriteLine(o)); Console.WriteLine(""); //os.Export(@"./orders.xml"); //Console.WriteLine("Import from ./orders.xml"); //OrderService os2 = new OrderService(); //os2.Import("./orders.xml"); //os2.Orders.ForEach(order => Console.WriteLine(order)); Console.ReadKey(); } catch (Exception e) { Console.WriteLine(e.Message); Console.WriteLine(e.StackTrace); } }