Unity DI not working in DI - default controller constructor called instead

Question

I am trying to get Unity Container Dependency Injection working on a self-hosted owin app. I have added the Unity nuget package to my project, and have set up my UnityConfig class as follows:

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<IDBContext,UniversalCoatingsDbContext>();
        container.RegisterType<IUserRepository,UserRepository>();

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

Then, I set up my controller like this:

public class UserController : ApiController
{
    private IUserRepository userRepo;

    public UserController() {
        Console.WriteLine("User controller default constructor");
    }

    //dependency injected value
    public UserController(IUserRepository repo)
    {
        this.userRepo = repo;
        Console.WriteLine("DI enabled constructor");
    }

    [HttpPost]
    public JsonResult<MessageResponse> Register(UnhashedUser unhashed_user)
    {
        MessageResponse response = new MessageResponse();
        if(ModelState.IsValid)
        {
            response = userRepo.createUser(unhashed_user);
        }
        else
        {
            response.message = "Invalid Request sent.";
        }

        return Json(response);

    }

}

The UnityConfig.RegisterComponents() method is called at the end of my Startup class's Configuration() method (after all the middleware is setup). When I access this controller's URL, the parameterless constructor is always called, and thus the instance of IUserRepository is never resolved.

Am I missing some sort of configuration pattern? Any info greatly appreciated.

Are you sure that you are setting the correct DependencyResolver? Take a look at this: damienbod.com/2013/10/01/self-host-webapi-with-owin-and-unity — Yacoub Massad
– Yacoub Massad, Commented Jul 23, 2016 at 21:35
Making the default constructor private made no difference (it still gets called. I know because the Console.WriteLine() statement in it is executing. — tutiplain
– tutiplain, Commented Jul 24, 2016 at 12:38

tutiplain · Accepted Answer · 2016-07-24 20:11:23Z

1

I modified my UnityConfig class to expose the container as a static variable. And then,

I added this to my startup class:

        //set up dependency injection
        UnityConfig.RegisterComponents();
        config.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(UnityConfig.container);
        app.UseWebApi(config);

answered Jul 24, 2016 at 20:11

tutiplain

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