应该是“DbContext”和“DbSet”暴露于纯POCO应用程序 [英] Should "DbContext" and "DbSet" be exposed for a pure POCO application

问题描述

有人可以启发我关于数据消费者不应该依赖EF（100％POCO）的DbContext和DbSet的预期（最佳实践）使用。虽然我发现的所有例子都解释了如何为底层数据源（通常对应于RDBMS表）创建POCO类，但它们仍然向外界公开DbContext和DbSet（包括MSFT自己关于如何进行数据绑定的示例与这些课）。这似乎打败了（严重）使用POCO的好处。 IOW，客户仍然受到EF的束缚，而不是一种更清洁（IMHO）的方法来创建一些在内部使用EF的数据存储项目，但仅向其用户公开了POCO。为什么EF上的所有文章似乎都忽视了这一点（我错过了一些东西）。谢谢。

解决方案

通常会创建一个使用DbContext的服务层（例如基于Repository模式）。它的作用是在数据库和应用程序/客户端之间进行调停。它将接受来自客户的POCO并将POCO返回给客户端。这样一来，客户端就知道存储库，但是它并不了解DbContext。

有些更多的阅读方式：

http://blogs.microsoft.co.il/blogs/gilf/archive/2010/01/20/using-repository-pattern-with-entity-framework.aspx

Can someone enlighten me about the intended (best-practice) use of "DbContext" and "DbSet" where data consumers should have no dependency on the EF whatsoever (100% POCO). While all the examples I find explain how to create POCO classes for the underlying data source (corresponding to RDBMS tables usually), they still expose "DbContext" and "DbSet" to the outside world (including MSFT's own examples on how to do data binding with these classes). This seems to defeat or (seriously) water down the benefits of using POCO. IOW, clients are still bound to the EF rather than a cleaner (IMHO) approach of creating some data store project that uses EF internally, but exposes only POCO to its users. Why do all articles on the EF seem to ignore this (am I missing something). Thanks.

解决方案

You would usually create a service layer (based on the Repository pattern for example) that makes use of DbContext. Its role is to mediate between the database and the application/client. It will accept POCOs from the client and return POCOs to the client. That way, the client knows about the repository, but it doesn't know anything about DbContext.

Some more reading for you:

http://blogs.microsoft.co.il/blogs/gilf/archive/2010/01/20/using-repository-pattern-with-entity-framework.aspx http://blogs.msdn.com/b/adonet/archive/2009/06/16/using-repository-and-unit-of-work-patterns-with-entity-framework-4-0.aspx

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