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 lt ISettingsManager  SettingsManager gt                      container RegisterType lt IMamDataManager  MamDataManager gt                      container RegisterType lt IAppsDataManager  AppsDataManager gt                      endregion                  if   isInitialize                                        isInitialize   true                                                      in my controller s code   ISettingsManager sm   mUnityContainer Resolve lt ISettingsManager gt       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 lt  gt  typeof ISettingsManager      but no use

User · Accepted Answer

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.

User · Answer

Below code will be helpful for you   public static IUnityContainer Initialise IUnityContainer container   null        if  container    null                container   new UnityContainer              container RegisterType lt ISettingsManager  SettingsManager gt         container Resolve lt SettingsManager gt         container RegisterType lt SettingsManagerController gt  new InjectionProperty   SettingManagerProvider   new ResolvedParameter lt ISettingManager gt           return container

User · Answer

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

User · Answer

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

User · Answer

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 lt ITestService  TestService gt                 RegisterTypes container         container   new UnityContainer          container RegisterType lt IProductRepository  ProductRepository gt             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

User · Answer

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 lt Imyinterfacename  myinterfaceimplclassname gt

User · Answer

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 lt IMapper gt  MappingConfig GetMapper    new HierarchicalLifetimeManager         container RegisterType lt IUserContext  UserContext gt  new TransientLifetimeManager       becomes  container RegisterInstance lt IMapper gt  MappingConfig GetMapper     container RegisterType lt IUserContext  UserContext gt       So that IMapper can be resolved successfully here   public class UserContext   BaseContext  IUserContext       public UserContext IMapper  mapper    base  mapper

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

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