How parameterless public constructor issue resolve in web api project

Question

My Asp.net mvc web api project have unity controller,it’s packages information is bellow

<package id="Unity" version="4.0.1" targetFramework="net451" />
<package id="Unity.Mvc" version="4.0.1" targetFramework="net451" />

After install those library from nuget manager I get two files in my App_Start folder they are respectively

1)  UnityConfig.cs
2)  UnityMvcActivator.cs

After write come content on my web api controller when I compile and run it’s show me bellow error.

{"$id":"1","Message":"An error has occurred.","ExceptionMessage":"An error occurred when trying to create a controller of type 'UserInfoController'. Make sure that the controller has a parameterless public constructor.","ExceptionType":"System.InvalidOperationException","StackTrace":" at-System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)\

To resolve this error, I used unity build in resolver in my UnityConfig.cs file syntax is bellow

    public static void RegisterTypes(IUnityContainer container)
    {
        container
           .RegisterType<IDataContextAsync, SmartHomeDataContext>(new PerRequestLifetimeManager())
           .RegisterType<IUnitOfWorkAsync, UnitOfWork>(new PerRequestLifetimeManager())
           .RegisterType<IVersionService, VersionService>()
           .RegisterType<IRepositoryAsync<Model.Models.Version>, Repository<Model.Models.Version>>()
           .RegisterType<IUserInfoService, UserInfoService>()
           .RegisterType<IRepositoryAsync<Model.Models.UserInfo>, Repository<Model.Models.UserInfo>>();

        DependencyResolver.SetResolver(new UnityDependencyResolver(container));
    }

Error is remaining,then I follow this article and try to use his manually create resolver.When I use article used resolver my application compiled with bellow error.

What should I do,how to solve this parameter less constructor issue.Will I need to use Unity web api nugget.

My Controller is bellow:

 public class UserInfoController : ApiController
    {
        private readonly IUnitOfWorkAsync _unitOfWorkAsync;
        private readonly IUserInfoService _userInfoService;
        public UserInfoController(IUnitOfWorkAsync unitOfWorkAsync, IUserInfoService userInfoService)
        {
            this._unitOfWorkAsync = unitOfWorkAsync;
            this._userInfoService = userInfoService;

        }
        [Route("api/Userinfos")]
        public HttpResponseMessage Get()
        {
            Mapper.CreateMap<UserInfo, UserInfoEntity>();
            var userInfos = _userInfoService.GetsUserInfos();
            HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, Mapper.Map<IEnumerable<UserInfo>, IEnumerable<UserInfoEntity>>(userInfos));
            return response;
        }
}

shamim shamim · Accepted Answer · 2016-01-18T05:48:30

Error message is descriptive,need to understand

System.Web.Http.Dependencies.IDependencyResolver (used by the Web API) and System.web.Mvc.IDependencyResolver (used by ASP.NET MVC) are two completely different types (even if they have the same name) and yet you attempt to assign both of them to the same type (UnityDependencyResolver) which obviously cannot work.

Please add bellow lines on your UnityConfig file

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

public static void RegisterTypes(IUnityContainer container)
        {
            container
                    .RegisterType<IDataContextAsync, SmartHomeDataContext>(new PerRequestLifetimeManager())
                    .RegisterType<IUnitOfWorkAsync, UnitOfWork>(new PerRequestLifetimeManager());

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

Where the first line is going to use the MVC DependencyResolver and in the second line I use the WebApi UnityDependencyResolver.

Note: Need to install Unity web api from nuget manager.

How parameterless public constructor issue resolve in web api project

1 Answers

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