MVC5 dependency injection issue

Question

I have created an application using MVC5 with the onion architecture approach. The solution contains 3 projects (core, infrastructure, and UI). The UI contains both Web API controllers and MVC controllers. The issue I’m running into is dependency injection. I have installed Unity.MVC5 & Unity.WebApi. My UnityConfig.cs under App_Start Looks like this:

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

        container.RegisterType<IPricingService, PricingService>();

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

My global.asax looks like this:

protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register);

        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);
        UnityConfig.RegisterComponents();

    }

To test out my controller, I defined my home controller like this:

private readonly IPricingService _pricingService;

    public HomeController(IPricingService PricingService)
    {
        this._pricingService = PricingService;
    }

When running home page I get No parameterless constructor defined for this object.

Now, moving to another test scenario, I created a web api controller and looks like this:

private readonly IPricingService _pricingService;

    public TestApiController(IPricingService PricingService)
    {
        this._pricingService = PricingService;
    }

Testing the web api generates this error:

An error occurred when trying to create a controller of type 'TextApiController'. Make sure that the controller has a parameterless public constructor.","exceptionType":"System.InvalidOperationException"

Not sure what I'm missing. Please advise.

NightOwl888 · Accepted Answer · 2018-01-30 22:26:21Z

1

You are supposed to inject the Unity.WebApi.DependencyResolver into the WebApi configuration not in GlobalConfiguration.Configuration.DependencyResolver.

public static void Register(HttpConfiguration config)
{
    var container = new UnityContainer();
    container.RegisterType<IProductRepository, ProductRepository>(new HierarchicalLifetimeManager());
    config.DependencyResolver = new UnityResolver(container);

    // Other Web API configuration not shown.
}

You also need to implement a child container in the BeginScope method as shown in this MSDN article.

edited Jan 30, 2018 at 22:26

answered Feb 20, 2015 at 19:06

NightOwl888

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3 Comments

Joe Over a year ago

Thanks for your comment, going to try that shortly.but what about the regular controller that generates the same error? Does this resolve both issues?

Joe Over a year ago

doesn't work. Can you provide an example that works with MVC5 + Web API? Thanks

Ahmad Shaman Virk Over a year ago

it works with MVC5 + Web API. But there is no need to install Unity.WebApi.DependencyResolver if Unity.MVC5 is installed. Thanks @nightowl888

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