EF6：必须包含在启动项目中吗？

Question

I have three projects: Persistence, Logic and Test.

The Persistence project has EF specific stuff. The Logic project makes use of a Repository pattern to interact with the Persistence/EF stuff. The Test project is a generic console that calls up a Logic object and checks that my EF setup is correct. Normal stuff.

In order to run this, I apparently need to have EF installed on the Test project (and I need to move/copy my App.Config from the EF class lib project to the Test project).

It's fine, it works, but when I get into other component/application layer projects, I don't want to have to include an entire EF reference for these "entry points" that don't ever deal with EF directly.

How to keep EF contained specifically to its "own" project? Thanks

edit for possible duplicate: the possible duplicate deals with how to decouple the business logic from the DAL. My question deals with why the presentation project requires a reference to Entity Framework: I already have the BAL/DAL segregated and a repository pattern in place.

Answer 1

Ideally you should limit the dependency of the Entity framework frame work to the minimum amount as possible. The best way to do it is to use EF only in the layer /Project where you have the data access code (Your Data access layer). It is better if you return DTO'/POCO's (Not Entities created by EF) to whoever calling those Data Access methods (Usually from Your Business Layer). You may keep this DTO's in a seperate project ( Let's call it YourProject.Common ). With this approach, you can always switch your DAL layer to use another data access approach (NHibernate , Pure ADO.NET etc..). If you are using Entity framework, You still need to keep the Connection string (for EF, with all those metadata stuff :( ) in your startup project.

So your Layers/Projects will be something like this

• Common ( Will have all the DTO/POCO's)

• DataAccess ( Will have the Data access code, This refer the YourProject.Common Project and return DTOs from that project. You don't need to keep the connection string in this project for your app to run as this will be called always from the startup project, which has the connection string. But, keep the App.Config (Generated by EF) as it is because you need that when you update your EDMX files later for db changes.

• Business ( BL layer, This project will have 2 project references, The Common Project and Data Access project)

• Web/Win forms ( This is your front end/Startup project. This will not directly talk to the Data Access, This will have 2 project references , Common and Data Access). This will have your connection string.