c# - 如何: Avoid Inserting Related Entities?

Question

我有这个模式:

http://img602.imageshack.us/img602/6978/schemac.png

我想在数据库中插入一个带有 OrderItems 的订单，所以我写了这个方法:

    public void SaveOrder(Order order)
    {
        using (var repository = new StoreEntities())
        {
            // Add order.
            repository.Orders.AddObject(order);

            // Add order items.
            foreach (OrderItem orderItem in order.OrderItems)
            {
                repository.OrderItems.AddObject(orderItem);
            }

            repository.SaveChanges();
        }
    }

一切都插入得很好，除了也插入了新的产品记录，这不是我想要的。

我想要的是插入 Order 及其 OrderItems，而无需在对象图中进一步向下移动。如何实现？

非常感谢任何帮助，谢谢。

Answer 1

当您在订单上调用 AddObject 时，对象图中的所有项目都被标记为已插入。因此，您必须将产品标记为未更改:

public void SaveOrder(Order order)     
{         
  using (var repository = new StoreEntities())         
  {             
    // Add order - calling add object marks Order and all entities in its 
    // object graph as Added - they will be inserted to database             
    repository.Orders.AddObject(order);              

    // You don't need to add order items because they should be added together 
    // with order

    // But you don't want to insert Products again, do you?
    // So you have to say that Products are not Added but Unchanged             
    foreach (var orderItem in order.OrderItems)             
    {                 
      // Not sure how to do it with your repository but with ObjectContext 
      // you can do
      // context.ObjectStateManager.ChangeObjectState(orderItem.Product, 
      //   EntityState.Unchanged);  
    }     
  }
}