Question

我有订单收集的客户。我有一些订单标识符，我需要添加到新的Customer实例中，如下所示：

var customer = new Customer();
customer.Orders.Add(new Order() { Id = 1 });
customer.Orders.Add(new Order() { Id = 2 });
customer.Orders.Add(new Order() { Id = 3 });

是否可以在不检索合适的订单实例的情况下进行？

Answer 1

是的，但是你必须按照正确的顺序进行。最简单的方法是：

var order1 = new Order { Id = 1 };
context.Orders.Attach(order1); // Now context knows the order and it tracks it as unchanged

var customer = new Customer();
context.Customers.AddObject(customer); // Now context knows the customer and it tracks it as a new

customer.Orders.Add(order1); // Now context knows about new relation between new customer and existing order

如果您按照示例中的说明进行操作，则会致电：

context.Customers.AddObject(customer);

和上下文将跟踪客户和所有相关订单作为新订单，因此您必须手动将所有订单的状态更改为不变，以避免重复插入：

foreach (var order in customer.Orders)
{
   if (order.Id != 0)
   {
       context.ObjectStateManager.ChangeObjectState(order, EntityState.Unchagned);
   }
}

添加到集合现有识别器

1 个答案: