ASP.NET MVC ActionFilterAttribute, IActionFilter Intercept Requests

    public class CustomActionFilter : ActionFilterAttribute, IActionFilter
    {
        void IActionFilter.OnActionExecuting(ActionExecutingContext filterContext)
        {
            Stopwatch tmr = new Stopwatch();
            tmr.Start();
            filterContext.HttpContext.Items["tmr"] = tmr;
            Debug.WriteLine(JsonConvert.SerializeObject(filterContext.ActionParameters));
        }

        void IActionFilter.OnActionExecuted(ActionExecutedContext filterContext)
        {
            Stopwatch tmr = (Stopwatch)filterContext.HttpContext.Items["tmr"];
            Debug.WriteLine(tmr.ElapsedMilliseconds);
        }
    }

        [CustomActionFilter]
        public ActionResult Index(string p1, string p2)
        {
            return Content(DateTime.Now.ToString());
        }