为什么我的EF4.1关系不会被置在一个空值赋值为null？ [英] Why does my EF4.1 relationship not get set to null upon assignment of a null value?

问题描述

在我的系统我有任务，可以有选择地分配给联系人。所以在我的业务逻辑，我有以下代码：

In my system I have tasks, which can optionally be assigned to contacts. So in my business logic I have the following code:

 if (_contactChanged) { task.Contact = contact; }

如果没有指定联系人，在联系人变量为空。这是的应该的以空出的接触关系时，我提交的变化，但是我已经注意到这是不会发生的我做了99％的时候（我已经看到它发生一次，但毕竟不能始终如一通过这个代码，一遍又一遍）步进。

If no contact was specified, the contact variable is null. This is supposed to null out the contact relationship when I submit changes, however I have noticed this isn't happening 99% of the time I do it (I have seen it happen once, but not consistently after stepping through this code over and over).

当我调试，我已经验证了 _contactChanged 是真正和里面的代码是不是击中。然而，当我踩过去 task.Contact =接触; 我注意到，虽然联系人为空， task.Contact 的类型

When I debug, I have verified that _contactChanged is true and the inside code isn't getting hit. However, after I step past task.Contact = contact; I notice that while contact is null, task.Contact is of type

{System.Data.Entity.DynamicProxies
.Contact_4DF70AA1AA8A6A94E9377F65D7B1DD3A837851FD3442862716FA7E966FFCBAB9}

和仍然依赖于它以前的数据。

and still has the previous data tied to it.

为什么代理没有被设置为null，我怎么能得到这个正常工作？

Why is the proxy not being set to null, and how can I get this to work properly?

推荐答案

哇。问得好。我能够证实/重​​现此，即使指涉不是动态代理。 t.Contact = NULL; 不起作用

Wow. Great question. I was able to confirm/reproduce this, even if the referent is not a dynamic proxy. t.Contact = null; doesn't work!

最佳答案我至今是说！

The best answer I have so far is to say:

    context.Entry(task).Reference(t => t.Contact).CurrentValue = null;

我真的很希望能有比这更好的办法，因为这是一些非常不方便语法

I'm really hoping that there is a better way than this, because this is some pretty inconvenient syntax.

更新：

本作品：

    var task = context.Tasks
        .Where(...your condition here...)
        .Include(t => t.Contact)
        .First();

    task.Contact = null;

或

如果你有一个（如在一个可为空的ContactID）在模型中定义的外键ID，这个就简单多了。

If you have a foreign key ID defined in your model (as in a nullable ContactId), this becomes a lot easier.

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