public Form1() { InitializeComponent(); OrderDetails OrderDetails1 = new OrderDetails("milk", 2, 3, 1); OrderDetails OrderDetails2 = new OrderDetails("hot dog", 3, 4, 2); OrderDetails OrderDetails3 = new OrderDetails("bread", 4, 5, 3); List <OrderDetails> OrderDetailss1 = new List <OrderDetails> { OrderDetails1, OrderDetails3 }; List <OrderDetails> OrderDetailss2 = new List <OrderDetails> { OrderDetails2, OrderDetails3 }; List <OrderDetails> OrderDetailss3 = new List <OrderDetails> { OrderDetails1, OrderDetails2 }; Order order1 = new Order(1, "a", OrderDetailss1); Order order2 = new Order(2, "aa", OrderDetailss2); Order order3 = new Order(3, "aaa", OrderDetailss3); os.add(order2); os.add(order1); os.add(order3); orderBindingSource.DataSource = os.MyOrder; }