我要创建其中有人问我创建的应用程序中的持久层的应用程序。该应用程序是在.NET。我已经创建了业务层和presentation层，但我不知道如何和为什么要创造持久层。

I have to create an application in which I am asked to create an persistence layer in the application. The application is in .net. I have created business layer and presentation layer but I don't know how and why to create persistence layer.

我一派，才知道，持久层用于存储和数据库通常检索数据。

I googled and came to know that persistence layer is used for storing and retrieving data usually from a database.

能详细解释一下别人？

推荐答案

为您打造一个DAL（数据访问层）或任何其他类型的数据库引擎和业务/应用逻辑之间的中间层的原因，就是加入这一层在你们之间从你使用的是现在特定的数据库引擎/技术隔离应用程序的其它部分/上层。

the reason for you to build a DAL ( Data Access Layer ) or any other kind of intermediate layer between database engine and Business / Application logic, is that by adding this layer in the between you isolate the rest / upper layers of your application from the specific database engine / technology you are using right now.

这有几个好处，像其他存储引擎更容易迁移，单层更好的封装数据库逻辑的（更容易替代或更新版本修改取决于如何以及你设计的跨层接口等）

This has several advantages, like easier migration to other storage engines, better encapsulation of database logic in a single layer ( easier to replace or modify later depending on how well you have designed your cross-layer interfaces etc...)

看我最受好评的答案在这里，它是关于ASP.NET MVC和EF，但解决方案和项目的结构的一个例子实际上是技术无关的：的 MVC3和实体框架

see my most rated answer here, it is an example about ASP.NET MVC and EF but the structuring of solution and projects is actually technology independent: MVC3 and Entity Framework

也读过一些文章，以便更好地理解这件事情，例如： http://www.developerfusion.com/article/84492/net-and-data-persistence/

Also read some articles to better understand this matter, for example: http://www.developerfusion.com/article/84492/net-and-data-persistence/