Api Controller有一个无参数公共构造函数错误

我正在使用Unity做我的DI，我遇到了以下错误:-

"尝试创建类型为'UploadController'的控制器时发生错误。确保控制器有一个无参数的公共构造函数。"

我有以下UnityResolver:-

public class UnityResolver : IDependencyResolver, IDependencyScope, System.Web.Http.Dependencies.IDependencyResolver
{
    protected IUnityContainer container;
    public UnityResolver(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }
    public object GetService(Type serviceType)
    {
        try
        {
            return container.Resolve(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return null;
        }
    }
    public IEnumerable<object> GetServices(Type serviceType)
    {
        try
        {
            return container.ResolveAll(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return new List<object>();
        }
    }
    public IDependencyScope BeginScope()
    {
        var child = container.CreateChildContainer();
        return new UnityResolver(child);
    }
    public void Dispose()
    {
        container.Dispose();
    }
}

}

我已经创建了一个UnityConfig如下:-

public static class UnityConfig
{
    public static void RegisterComponents()
    {
        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>();
        BuildUnityContainer();
        GlobalConfiguration.Configuration.DependencyResolver = new UnityDependencyResolver(container);
    }
    private static IUnityContainer BuildUnityContainer()
    {
        var container = new UnityContainer();
        // register all your components with the container here
        // you don't need to register controllers
        container.RegisterType<IFileHelpers, FileHelpers>();
        container.RegisterType<IDatabaseHelper, DatabaseHelper>();
        container.RegisterType<IPlayersHelpers, PlayersHelpers>();
        container.RegisterType<IBaseRepository, BaseRepository>();
        container.RegisterType<IAttribsRepository, AttribsRepository>();
        container.RegisterType<IPlayerRepository, PlayerRepository>();
        container.RegisterType<IFileRepository, FileRepository>();
        container.RegisterType<IPlayerAttribsRepository, PlayerAttribsRepository>();
        container.RegisterType<FMContext>();
        container.RegisterType<UserManager<ApplicationUser>>(new HierarchicalLifetimeManager());
        container.RegisterType<IUserStore<ApplicationUser>, UserStore<ApplicationUser>>(new HierarchicalLifetimeManager());
        return container;
    }
}

}

我正在初始化WebApiConfig.cs中的所有内容

    public static void Register(HttpConfiguration config)
    {
        // Web API configuration and services
        // Configure Web API to use only bearer token authentication.
        config.SuppressDefaultHostAuthentication();
        config.Filters.Add(new HostAuthenticationFilter(OAuthDefaults.AuthenticationType));
        // Web API configuration and services
        var container = new UnityContainer();
        UnityConfig.RegisterComponents();
        config.DependencyResolver = new UnityResolver(container);
        config.EnableCors();
        // Web API routes
        config.MapHttpAttributeRoutes();
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }
}

这是我的UploadController类-

    public class UploadController : ApiController
{
    private readonly IFileHelpers _fileHelpers;
    private readonly IDatabaseHelper _databaseHelper;
    private readonly IPlayersHelpers _playersHelpers;
    public UploadController(IFileHelpers fileHelpers, IDatabaseHelper databaseHelper, IPlayersHelpers playersHelpers)
    {
        _fileHelpers = fileHelpers;
        _databaseHelper = databaseHelper;
        _playersHelpers = playersHelpers;
    }
    public async Task<HttpResponseMessage> Post()
    {........................}

你能帮我确定我做错了什么吗?我还需要声明些什么吗?

感谢您的帮助和时间

// ...
// Web API configuration and services
var container = new UnityContainer();
UnityConfig.RegisterComponents();
config.DependencyResolver = new UnityResolver(container);