实体对象不能被IEntityChangeTracker的多个实例引用 [英] An entity object cannot be referenced by multiple instances of IEntityChangeTracker

问题描述

我使用EF作为ORM。

I use EF as ORM.

我在每个请求上处理 objectContext 。

我将这些实体保存在缓存层，因为我的服务获得了很多流量。

I save the entities in a cache layer, as my service gets lots of traffic.

我有时得到错误 objectContext已经处理了对于我从缓存获得的某些实体。

I got sometimes get the error objectContext already disposed for some entities that I got from the cache.

我已经将这段代码添加到被从缓存

I have added this code to elements that were retrived from the cache

if (maMDBEntities.Entry(group).State == EntityState.Detached)
{
    maMDBEntities.Groups.Attach(group);
}

但现在我有时会得到这个错误：

but now I sometimes get this error:

实体对象不能被IEntityChangeTracker的多个实例引用。

An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

使用 Attach（）一个不正确的解决方案？

Was using Attach() an incorrect solution from the first place?

推荐答案

正如我们在你的另一个问题（将EF :: attach（实体）将解决objectContext已经被隐藏了吗？），你必须在将实体附加到另一个上下文之前分离实体！

As we told you in your other question (will EF::attach(entity) will solve objectContext is already desposed?), you have to detach the Entities before attaching it to another Context!

如果 maMDBEntities 是一个新的上下文（不是加载数据的上下文），EntityState不会从此Contexts视点附加。所以你的支票是不够的。

If maMDBEntities is a new Context (not the one, which loaded the data), the EntityState is not "attached" from this Contexts point-of-view. So your check is not sufficient.

这个 maMDBEntities.Entry（group）.State == EntityState.Detached 将永远对于没有加载实体的上下文是正确的。

This maMDBEntities.Entry(group).State == EntityState.Detached will always be true for an Context, which did not load the Entity.

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