ControllerBuilder.Current.SetControllerFactory(controllerFactory)

(参考：http://www.dotnetcurry.com/ShowArticle.aspx?ID=786)

现在我的问题是：

如何为IHttpControllerActivator派生类设置工厂？

我们有ASP.NET MVC 4.0中的东西,像：

HttpControllerBuilder.Current.SetApiControllerActivator(httpControllerActivator)

？

更新：

我想添加我当前的代码,可能有助于了解情况：

我定制的HttpControllerActivator：

public class MyCustomApiActivator : DefaultHttpControllerActivator 
                                    //or IHttpControllerActivator ?
{
    private readonly Dictionary<string,Func<HttpRequestMessage,IHttpController>> _apiMap;

    public MyCustomApiActivator(IMyRepository repository)
    {
        if (repository == null)
        {
            throw new ArgumentException("repository");
        }
        _apiMap = new Dictionary<string,IHttpController>>();
        controllerMap["Home"] = context => new HomeController();
        _apiMap["MyCustomApi"] = context => new MyCustomApiController(repository);
    }

    public IHttpController Create(HttpRequestMessage request,HttpControllerDescriptor controllerDescriptor,Type controllerType)
    {
        if(_apiMap.ContainsKey(controllerType.Name))
            return _apiMap[controllerType.Name](request);
        return null;
    }
}

我的组成根：

public class CompositionRoot
{
    private readonly IHttpControllerActivator _apiControllerActivator;

    public CompositionRoot()
    {
        _apiControllerActivator = CompositionRoot.CreateHttpControllerActivator();
    }

    public IHttpControllerActivator ApiControllerActivator
    {
        get { return _apiControllerActivator; }
    }

    private static IHttpControllerActivator CreateHttpControllerActivator()
    {
        string defaultRepositoryTypeName = ConfigurationManager.AppSettings["DefaultRepositoryTypeName"];
        var defaultRepositoryType = Type.GetType(defaultRepositoryTypeName,true);
        var defaultRepository = (IMyRepository)Activator.CreateInstance(defaultRepositoryType);

        var apiController = new MyCustomApiActivator(defaultRepository);
        return apiController;
    }
}

最后这是在我的Global.asax.cs里面,我需要一个技巧：

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

        WebApiConfig.Register(GlobalConfiguration.Configuration);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);


        var root = new CompositionRoot();
        //The following line raise this compile-time error:
        // cannot convert from 'System.Web.Http.Dispatcher.IHttpControllerActivator' 
        //                to 'System.Web.Mvc.IControllerFactory'
        ControllerBuilder.Current.SetControllerFactory(root.ApiControllerActivator);
    }