CODEWITHSUNDEEP
asp.net-mvcdependency-injectionninject
lloydphillips
lloydphillips

Reputation: 2855

Dependency on a service layer with Ninject and MVC

I've got a problem with a bog standard three tier project using MVC that I'm trying to use Ninject with. I've got a MemberRepository:

public class MemberRepository : IMemberRepository{
     public bool Save(Member member){
          //saves member
     }
}

I then have my Service Layer:

public class MemberService : IMemberService{
     public bool Register(string email){
        //Do Stuff & Populate Member Object
        _repo.Save(member);
     }
}

Given I'll be using Ninject what is the best way of me setting up my AccountController. Should I pass in the MemberService to the constructor like so:

public class AccountController : Controller
{
    IMemberService _memberService;

    public AccountController(IMemberService memberService)
    {
        _memberService = memberService;
    }
}

Or pass in the repository:

public class AccountController : Controller
{
    IMemberService _memberService;

    public AccountController(IMemberRepository memberRepo)
    {
        _memberService = new MemberService(memberRepo);
    }
}

Or Both?

I originally had just a repository (no service layer) but I've had to implement a service layer and I'm not sure how I'd handle the 'dependency' when registering the kernal in my NinjectWebCommon.cs file. Which was originally just this:

    kernel.Bind<IMemberRepository>().To<SqlMemberRepository>();

But now I'm wondering if I need to register the IMemberService and have the repo as some kind of parameter.

:s Feeling kind of lost. Hope I'm making sense and someone can help out.

Upvotes: 3

Views: 1568

Answers (1)

Ian Routledge
Ian Routledge

Reputation: 4042

I've never used Ninject, I've been using Unity, but the same principles exist so hopefully this might help.

The service layer is the thing that is exposed to the controller - the controller needs to know nothing about the underlying repository. The flow is as follows, and each layer doesn't know about the layers above it:

Controller -> Service > Repository

So I would go with option 1, and then inject the repository into the constructor of the service.

public class MemberService : IMemberService {
     private readonly IMemberRepository _repo;

     [Inject]
     public MemberService (IMemberRepository repo){
        this._repo = repo;
     }

     public bool Register(string email){
        //Do Stuff & Populate Member Object
        _repo.Save(member);
     }
}

and

public class AccountController : Controller
{
    private readonly IMemberService _memberService;

    [Inject]
    public AccountController(IMemberService memberService)
    {
        _memberService = memberService;
    }
}

That example obviously uses constructor injection but you can use property/field injection if you want instead. When you register your dependencies, you'll have to register both:

kernel.Bind<IMemberRepository>().To<SqlMemberRepository>();
kernel.Bind<IMemberService>().To<MemberService>();

Upvotes: 6

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