Exception is: InvalidOperationException - The current type, is an interface and cannot be constructed. Are you missing a type mapping?

Question

In my bootstrapper:

namespace Conduit.Mam.ClientServices.Common.Initizliaer
{
    public static class Initializer
    {
        private static bool isInitialize;
        private static readonly object LockObj = new object();
        private static IUnityContainer defaultContainer = new UnityContainer();

        static Initializer()
        {
            Initialize();
        }

        public static void Initialize()
        {
            if (isInitialize)
                return;

            lock (LockObj)
            {
                IUnityContainer container = defaultContainer;

                //registering Unity for MVC
                DependencyResolver.SetResolver(new UnityDependencyResolver(container));

                //registering Unity for web API
                //  GlobalConfiguration.Configuration.DependencyResolver = new Unity.WebApi.UnityDependencyResolver(container);

                #region managers
                container.RegisterType<ISettingsManager, SettingsManager>();

                container.RegisterType<IMamDataManager, MamDataManager>();

                container.RegisterType<IAppsDataManager, AppsDataManager>();
                #endregion

                if (!isInitialize)
                {
                    isInitialize = true;
                }
            }
        }
    }
}

in my controller's code:

ISettingsManager sm = mUnityContainer.Resolve<ISettingsManager>();

hovering on mUnityContainer I see ISettingsManager is mapped to SettingsManager

but then I get the error:

Exception is: InvalidOperationException - The current type, is an interface and cannot be constructed. Are you missing a type mapping?

I have also tried

ISettingsManager sm = (ISettingsManager)mUnityContainer.Resolve<>(typeof(ISettingsManager));

but no use

Answer 1

Just for others (like me) who might have faced the above error. The solution in simple terms.

You might have missed to register your Interface and class (which implements that inteface) registration in your code.

e.g if the error is
"The current type, xyznamespace. Imyinterfacename, is an interface and cannot be constructed. Are you missing a type mapping?"

Then you must register the class which implements the Imyinterfacename in the UnityConfig class in the Register method. using code like below

 container.RegisterType<Imyinterfacename, myinterfaceimplclassname>();

Answer 2

You are incorrectly using Dependency Injection. The proper way is to have your controllers take the dependencies they need and leave to the dependency injection framework inject the concrete instances:

public class HomeController: Controller
{
    private readonly ISettingsManager settingsManager;
    public HomeController(ISettingsManager settingsManager)
    {
        this.settingsManager = settingsManager;
    }

    public ActionResult Index()
    {
        // you could use the this.settingsManager here
    }
}

As you can see in this example the controller doesn't know anything about the container. And that's how it should be.

All the DI wiring should happen in your Bootstraper. You should never use container.Resolve<> calls in your code.

As far as your error is concerned, probably the mUnityContainer you are using inside your controller is not the same instance as the one constructed in your Bootstraper. But since you shouldn't be using any container code in your controllers, this shouldn't be a problem anymore.

Answer 3

In my case, I was getting this error despite registering an existing instance for the interface in question.

Turned out, it was because I was using Unity in WebForms by way of the Unity.WebForms Nuget package, and I had specified a Hierarchical Lifetime manager for the dependency I was providing an instance for, yet a Transient lifetime manager for a subsequent type that depended on the previous type - not usually an issue - but with Unity.WebForms, the lifetime managers work a little differently... your injected types seem to require a Hierarchical lifetime manager, but a new container is still created for every web request (because of the architecture of web forms I guess) as explained excellently in this post.

Anyway, I resolved it by simply not specifying a lifetime manager for the types/instances when registering them.

i.e.

container.RegisterInstance<IMapper>(MappingConfig.GetMapper(), new HierarchicalLifetimeManager());    
container.RegisterType<IUserContext, UserContext>(new TransientLifetimeManager());

becomes

container.RegisterInstance<IMapper>(MappingConfig.GetMapper());
container.RegisterType<IUserContext, UserContext>();

So that IMapper can be resolved successfully here:

public class UserContext : BaseContext, IUserContext
{
    public UserContext(IMapper _mapper) : base(_mapper)
    {

    }
    ...
}

Answer 4

May be You are not registering the Controllers. Try below code:

Step 1. Write your own controller factory class ControllerFactory :DefaultControllerFactory by implementing defaultcontrollerfactory in models folder

  public class ControllerFactory :DefaultControllerFactory
    {
    protected override IController GetControllerInstance(RequestContext         requestContext, Type controllerType)
        {
            try
            {
                if (controllerType == null)
                    throw new ArgumentNullException("controllerType");

                if (!typeof(IController).IsAssignableFrom(controllerType))
                    throw new ArgumentException(string.Format(
                        "Type requested is not a controller: {0}",
                        controllerType.Name),
                        "controllerType");

                return MvcUnityContainer.Container.Resolve(controllerType) as IController;
            }
            catch
            {
                return null;
            }

        }
        public static class MvcUnityContainer
        {
            public static UnityContainer Container { get; set; }
        }
    }

Step 2:Regigster it in BootStrap: inBuildUnityContainer method

private static IUnityContainer BuildUnityContainer()
    {
      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>();    
      //RegisterTypes(container);
      container = new UnityContainer();
      container.RegisterType<IProductRepository, ProductRepository>();


      MvcUnityContainer.Container = container;
      return container;
    }

Step 3: In Global Asax.

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

            WebApiConfig.Register(GlobalConfiguration.Configuration);
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);
            AuthConfig.RegisterAuth();
            Bootstrapper.Initialise();
            ControllerBuilder.Current.SetControllerFactory(typeof(ControllerFactory));

        }

And you are done

Answer 5

In my case, I have used 2 different context with Unitofwork and Ioc container so i see this problem insistanting while service layer try to make inject second repository to DI. The reason is that exist module has containing other module instance and container supposed to gettng a call from not constractured new repository.. i write here for whome in my shooes

Answer 6

I had this problem, and the cause was that I had not added the Microsoft.Owin.Host.SystemWeb NuGet package to my project. Although the code in my startup class was correct, it was not being executed.

So if you're trying to solve this problem, put a breakpoint in the code where you do the Unity registrations. If you don't hit it, your dependency injection isn't going to work.

Answer 7

Below code will be helpful for you

public static IUnityContainer Initialise(IUnityContainer container = null)
{
    if (container == null)
    {
        container = new UnityContainer();
    }
    container.RegisterType<ISettingsManager, SettingsManager>();
    container.Resolve<SettingsManager>();
    container.RegisterType<SettingsManagerController>(new InjectionProperty("_SettingManagerProvider", new ResolvedParameter<ISettingManager>()));
    return container;
}