I have 4 Projects in a solution
- DAL_Project
- BLL_Project
- Interface_Project
- WebApi_Project
Interface_Project has two interfaces ICar_DAL and ICar_BLL
DAL_Project has a class Car_DAL that implements ICar_DAL
BLL_Project has a class Car_BLL that implements ICar_BLL and its constructor takes in ICar_DAL
WebApi_Project has an api controller CarApiController and its constructor takes in ICar_BLL
the dependency resolution of WebApi Controller's constructor is done by Unity.WebApi using this in Bootstrapper.cs:
container.RegisterType<ICar_BLL, Car_BLL>();
this would have worked if my Car_BLL further didn't require ICar_DAL in its constructor.
to make it work i can do some thing like this:
container.RegisterType<ICar_BLL, Car_BLL>();
container.RegisterType<ICar_DAL, Car_DAL>();
but that would mean that i need to add reference to DAL_Project in my WebApi_Project which is something i would never want to do. DAL_Project should only be referred by BLL_Project
How can i solve this issue?
but that would mean that i need to add reference to DAL_Project in my
WebApi_Project which is something i would never want to do.
Oh you seem to have some misunderstanding about how Dependency should be done if you don't want to do that. The DI container is configured in the outermost layer of your application which is actually the host. It is also referred to as the Composition Root. In your case this is the hosting application of your Web API. If you are using ASP.NET to host your Web API then this is the right place to do the composition root and reference all the other underlying projects.
Personally in complex project I tend to have a ProjectName.Composition class library which serves me as a Composition root. this is where I configure my DI container and this is the project that references all the others - coz obviously in order to configure your DI root you need all the dependent projects and implementations. This .Composition assembly is then references in the hosting application and the Bootstrapper.Initialize method called in the Initialize method of the hosting application.
- In the case of ASP.NET host that would be
Application_Start in Global.asax
- In case of a desktop application or a self-host that would be the
Main method which is the entry point.
