EF4：POCO，自我跟踪实体，POCO代理之间的差异 [英] EF4: Difference between POCO , Self Tracking Entities , POCO Proxies

问题描述

有人可以指出POCO，自我跟踪实体，POCO代理之间的区别？

实际上，我正在使用Entity Framework 4.0和POCO（Repository Pattern）我在POCO中做了一些修改，并调用ObjectContext.Savechanges，然后将其反映到DB。
我的问题是，

1. 由于没有跟踪数据库，上下文是否将更改保留到数据库？


2. 上下文是否为POCO生成跟踪信息？

我正在使用的示例代码， / p>

  IEFRepository< Category> catRepository = new EFRepository< Category>（）; 
类别c = catRepository.FindOne< Category>（x => x.Name ==Paper）; 
 
 c.Name =纸; 
 catRepository.SaveChanges（System.Data.Objects.SaveOptions.None）; 
  

解决方案

自我跟踪实体不是POCO。相反，他们非常坚持认识。甚至比 EntityObject 实体。什么使它们独一无二的是即使没有附加到 ObjectContext 也可以跟踪更改。

纯正如你所说，POCO使得变更跟踪变得困难。真的，唯一可以做的是比较对象的快照。对象上下文有一个 DetectChanges 方法。

使用伪POCO代理，您真正拥有的是一种在编译时看起来像几乎像POCO的类型，并且像运行时的​​非POCO一样。我说几乎，因为在运行时你会得到一个实例，它是一个编译时类型的子类型。因此，您要跟踪更改的任何属性必须是非私有的和虚拟的。类似的限制适用于延迟加载。您可以在中阅读更多信息这一系列文章在ADO.NET团队博客上。

Can someone point me the difference between POCO , Self Tracking Entities , POCO Proxies?

Actually, I am working Entity Framework 4.0 and POCO(Repository Pattern) and whenever I do some changes in the POCO and call ObjectContext.Savechanges then it reflects to the DB. My question is,

1. How does the Context persist the change to the DB since it is not tracked?
2. Does the Context generates the tracking info on the fly for POCO?

Sample Code I am using,

        IEFRepository<Category> catRepository = new EFRepository<Category>();
        Category c = catRepository.FindOne<Category>(x => x.Name == "Paper");

        c.Name = "Paper";
        catRepository.SaveChanges(System.Data.Objects.SaveOptions.None);

解决方案

Self tracking entities are not POCOs. On the contrary, they are very much persistence-aware. More so than EntityObject entities, even. What makes them unique is the changes can be tracked even when they are not attached to an ObjectContext.

"Pure" POCOs, as you say, make change tracking difficult. Really, the only thing you can do is compare snapshots of the object. The object context has a DetectChanges method for this.

With a pseudo-POCO proxy, what you really have is a type which looks (almost) like a POCO at compile time and like a non-POCO at runtime. I say "almost" because at runtime you will get an instance which is a subtype of the compile-time type. Because of this, any properties for which you want to track changes must be non-private and virtual. Similar restrictions apply to lazy loading. You can read more about this in this series of articles on the ADO.NET team blog.

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