private void Form1_Load(object sender, EventArgs e) { orderService = new OrderService.OrderService(); OrderService.Order order = new Order(1, "a", new List <OrderItem>()); order.AddItem(new OrderService.OrderItem(1, "apple", 100.0, 10)); orderService.AddOrder(order); OrderService.Order order2 = new Order(2, "b", new List <OrderItem>()); order2.AddItem(new OrderService.OrderItem(1, "applepen", 100.0, 10)); orderService.AddOrder(order2); orderBindingSource.DataSource = orderService.Orders; }