CODEWITHSUNDEEP
c#asp.net-mvcentity-frameworkdependency-injectionninject
Brian Ogden
Brian Ogden

Reputation: 19232

Accessing Concrete Implementation of Interface, Dependency Injection

So I am using Entity Framework, I will not be using the repository pattern, please don't suggest it.

I am trying to create a child context that inherits from System.Data.Entity.DbContext and also using dependency injection so I need an interface and a concrete implementation.

The interface:

    public interface IHomeUpContext
    {
        void Test();
    }

My Entity Framework generated context:

public partial class HomeUpEntities : DbContext
...

My context base class:

 public class HomeUpContext : HomeUpEntities, IHomeUpContext
 {
    public override int SaveChanges()
    {
        return base.SaveChanges();
    }

    public void Test()
    {

    }
 }

And I have the following MVC Base Controller:

public class BaseController: Controller
{
    public IHomeUpContext Context { get; set; }         
}

And then my child controller:

    public class HomeController : BaseController
    {
        public HomeController(IHomeUpContext context)
        {
            Context = context;
        }

        public ActionResult Index()
        {
            //complex queries encapsulated
            var query = new ListPostsQuery(Context);

            var posts = query.Execute(0, 10);

            var postsViewModel = Mapper.Map<List<Post>, List<PostViewModel>>(posts);

            return View(postsViewModel);
        }

        [HttpPost]
        public ActionResult Edit(PostViewModel model)
        {
            var post = Context. //Only Test() method available here because my interface only defines that Method.

         }

Obviously, I am doing dependency injection. In my HomeController.Edit method I want to be able to:

 var post = Context.MyTable.Where(item => item.PostId == model.PostId);

I would have to define a bunch of stuff in my IHomeContext to do this. So now I will have to cast my injected concrete implementation of IHomeUpContext to HomeUpContext in my controller. No bueno.

Again I will not be using the Repository Pattern and a Unit of Work pattern, I firmly believe it is a leaky abstraction 9 times out of 10 and an "ever-spiraling Repository API": http://www.wekeroad.com/2014/03/04/repositories-and-unitofwork-are-not-a-good-idea/

I want to use dependency injection, encapsulate complex queries but do simple Context save update and get by id directly in my controller. But having to cast my IHomeUpContext to a concrete instance defeats the purpose of the dependency injection.

Upvotes: 1

Views: 663

Answers (1)

krivtom
krivtom

Reputation: 24916

In this case if you don't want to use repository pattern (which I understand you don't) then you have to expose all DataSets in the interface as well:

public interface IHomeUpContext
{
    DbSet<channel> channel { get; set; }
    int SaveChanges();
}

Upvotes: 0

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