asp.net mvc HandleErrorAttribute 异常错误处理 无效！

系统未知bug，代码没有深究。 

现象：filters.Add(new HandleErrorAttribute()); 使用了全局的异常处理过滤。

HandleErrorAttribute 核心代码：

public virtual void OnException(ExceptionContext filterContext)
        {
            if (filterContext == null)
            {
                throw new ArgumentNullException("filterContext");
            }
            if (filterContext.IsChildAction)
            {
                return;
            }
            if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)
            {
                return;
            }
            Exception exception = filterContext.Exception;
            if (new HttpException(null, exception).GetHttpCode() != 500)
            {
                return;
            }
            if (!this.ExceptionType.IsInstanceOfType(exception))
            {
                return;
            }
            string controllerName = (string)filterContext.RouteData.Values["controller"];
            string actionName = (string)filterContext.RouteData.Values["action"];
            HandleErrorInfo model = new HandleErrorInfo(filterContext.Exception, controllerName, actionName);
            filterContext.Result = new ViewResult
            {
                ViewName = this.View,
                MasterName = this.Master,
                ViewData = new ViewDataDictionary<HandleErrorInfo>(model),
                TempData = filterContext.Controller.TempData
            };
            filterContext.ExceptionHandled = true;
            filterContext.HttpContext.Response.Clear();
            filterContext.HttpContext.Response.StatusCode = 500;
            filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
        }

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