WebApi AuthorizationFilterAttribute: ActionArguments are emp

我正在为WebApi控制器实现AuthorizationFilterAttribute，但我似乎无法访问传递到控制器的参数：

在MVC4中，这很好：

public class MyMVCController : Controller
{
    [CanAccessMyResourceApi]
    public MyViewModel Get(int id)
    {
       //...
    }
}
public class CanAccessMyResourceMVCAttribute : CanAccessAttributeBase
{
   public override void OnAuthorization(AuthorizationContext filterContext)
   {
       var param = filterContext.Controller.ValueProvider.GetValue("id")
       /// ... 
   }
}

但在WebAPI中，我认为参数应该在ActionArguments中，但这里的"param"是空的：

public class MyWebApiController : ApiController
{
   [CanAccessMyResourceWebApi]
   public MyViewModel Get(int id)
   {
      //...
   }
}
public class CanAccessMyResourceWebApiAttribute : AuthorizationFilterAttribute 
{
    public override void OnAuthorization(HttpActionContext filterContext)
    {       
        // the debugger shows that ActionArguments is empty:
        var param = filterContext.ActionArguments["id"]
        /// ...
    }
}

正在传递到控制器的参数在其他地方可用吗？（当我删除过滤器属性时，我验证了控制器的操作是否正确地获得了Id值。）

var variable = HttpContext.Current.Request.Params["parameterName"];
public class CustomAuthorizeAttribute : AuthorizeAttribute
  {
     protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext)
     {
        var clientId = actionContext.ControllerContext.RouteData.Values["clientid"];
     }
  }