ASP.NETMVC5中的Actionfilter注入

我有一个简单的过滤器.

public class IsAdmin : ActionFilterAttribute, IAuthenticationFilter
{
    private string _roleName;
    IBusinessIdentity _identity;

    public IsAdmin(string roleName, IBusinessIdentity identity)
    {
        this._roleName = roleName;
        this._identity = identity;
    }

    public void OnAuthentication(AuthenticationContext filterContext)
    {
    }

    public void OnAuthenticationChallenge(AuthenticationChallengeContext filterContext)
    {
        if (!_identity.Roles.Contains(_roleName))
            filterContext.Result = new HttpUnauthorizedResult();
    }
}

public class HomeController : Controller
{
    readonly IBusinessIdentity _identity;

    public HomeController(IBusinessIdentity identity)
    {
        this._identity= identity;
    }

    [IsAdmin("Admin", _identity)]
    public ActionResult Index()
    {
        return View();  
    }
}

using Ninject.Web.Mvc.FilterBindingSyntax;