Cannot create an instance of an Interface with Unity

Question

I have my MVC5 Web controller and trying to do a dependency injection using:

public class PatientsController : Controller
    {
        public ISomeRepository _repo;
        // GET: Patients
        public ActionResult Index(ISomeRepository repo)
        {
            _repo = repo;
            return View();
        }
    }

My Unity configuration looks like following:

public static class UnityConfig
    {
        public static void RegisterComponents()
        {
            var container = new UnityContainer();

            // register all your components with the container here
            // it is NOT necessary to register your controllers

            // e.g. container.RegisterType<ITestService, TestService>();
            container.RegisterType<ISomeRepository, SomeRepository>();

            //  GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
            GlobalConfiguration.Configuration.DependencyResolver = new UnityResolver(container);
        }

But when I am navigating to controller, getting error:

[MissingMethodException: Cannot create an instance of an interface.]

You inject repo into the controller constructor.

Jasen
– Jasen

2017-08-01 01:41:02 +00:00
Commented Aug 1, 2017 at 1:41 — Jasen
– Jasen, Commented Aug 1, 2017 at 1:41

Philipp Grathwohl · Accepted Answer · 2017-08-10 06:27:54Z

6

You should use constructor injection in your controller instead of injecting the instance in your action.

public class PatientsController : Controller
{
   private ISomeRepository _repo;

   public PatientsController(ISomeRepository repo) 
   { 
      _repo = repo;
   }        

   public ActionResult Index()
   {
      // use _repo here
      return View();
   }
}

edited Aug 10, 2017 at 6:27

answered Aug 1, 2017 at 1:41

Philipp Grathwohl

2,8763 gold badges28 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Cannot create an instance of an Interface with Unity

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related