CODEWITHSUNDEEP
c#asp.net-web-apidependency-injectionautofac
Aniruddha
Aniruddha

Reputation: 1039

Create Controller Failure stating that the controller needs a parameterless public constructor

Create Controller Failure of type 'UserController'. Make sure that the controller has a parameterless public constructor

Using AutoFac, I have registered UnitOfWork repository as below, also I'm pasting controller code and stack trace. Please assist. Unable to understand as why controller requires parameterless public costructor.

private static IContainer RegisterServices(ContainerBuilder builder)
        {
            //Register your Web API controllers.  
            builder.RegisterApiControllers(Assembly.GetExecutingAssembly());

            builder.RegisterType<UserContext>().As<DbContext>().InstancePerRequest();
            builder.RegisterType<DBFactory>().As<IDBFactory>().InstancePerRequest();
            builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().InstancePerRequest();
            builder.RegisterGeneric(typeof(GenericRepo<>)).As(typeof(IGenericRepo<>)).InstancePerRequest();

            //Set the dependency resolver to be Autofac.  
            Container = builder.Build();

            return Container;
        }  

private readonly IUnitOfWork _unitofwork;
        public UserController(IUnitOfWork uow)
        {
            _unitofwork = uow;
        }
        [HttpGet]
        public IEnumerable<UserDetail> UserData()
        {
            return _unitofwork.userDetail.GetAllUsers();
        }

StackTrace

  at Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext context, IEnumerable`1 parameters)
       at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable`1 parameters)
       at Autofac.Core.Resolving.InstanceLookup.<Execute>b__0()
       at Autofac.Core.Lifetime.LifetimeScope.GetOrCreateAndShare(Guid id, Func`1 creator)
       at Autofac.Core.Resolving.InstanceLookup.Execute()
       at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.Core.Resolving.InstanceLookup.ResolveComponent(IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.Core.Activators.Reflection.AutowiringParameter.<>c__DisplayClass2.<CanSupplyValue>b__0()
       at Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate()
       at Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext context, IEnumerable`1 parameters)
       at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable`1 parameters)
       at Autofac.Core.Resolving.InstanceLookup.Execute()
       at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.Core.Resolving.ResolveOperation.ResolveComponent(IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.Core.Resolving.ResolveOperation.Execute(IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.Core.Lifetime.LifetimeScope.ResolveComponent(IComponentRegistration registration, IEnumerable`1 parameters)
       at Autofac.ResolutionExtensions.TryResolveService(IComponentContext context, Service service, IEnumerable`1 parameters, Object& instance)
       at Autofac.ResolutionExtensions.ResolveOptionalService(IComponentContext context, Service service, IEnumerable`1 parameters)
       at Autofac.ResolutionExtensions.ResolveOptional(IComponentContext context, Type serviceType, IEnumerable`1 parameters)
       at Autofac.ResolutionExtensions.ResolveOptional(IComponentContext context, Type serviceType)
       at Autofac.Integration.WebApi.AutofacWebApiDependencyScope.GetService(Type serviceType)
       at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.GetInstanceOrActivator(HttpRequestMessage request, Type controllerType, Func`1& activator)
       at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)

Controller:

public class UserController : ApiController
{
  private readonly IUnitOfWork _unitofwork;
  public UserController(IUnitOfWork uow)
  {
      _unitofwork = uow;
  }

  [HttpGet]
  public IEnumerable<UserDetail> UserData()
  {
      return _unitofwork.userDetail.GetAllUsers();
  }
}

Upvotes: 2

Views: 254

Answers (2)

Aniruddha
Aniruddha

Reputation: 1039

Issue was due to wrong setup of IDbFactory.

Upvotes: -1

Erik Philips
Erik Philips

Reputation: 54638

As stated in the documentation, you need set the dependency resolver:

After building your container pass it into a new instance of the AutofacWebApiDependencyResolver class. Attach the new resolver to your HttpConfiguration.DependencyResolver to let Web API know that it should locate services using the AutofacWebApiDependencyResolver. This is Autofac’s implementation of the IDependencyResolver interface.

var container = builder.Build();
config.DependencyResolver = new AutofacWebApiDependencyResolver(container);

I can tell you aren't doing this because the stacktrace specifically states which resolver it's using to create controllers:

System.Web.Http.Dispatcher.DefaultHttpControllerActivator.GetInstanceOrActivator(HttpRequestMessage request, Type controllerType, Func`1& activator)

Upvotes: 3

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