http - 在 mvc 应用程序中看不到 ETag 标头

Question

我想玩动作过滤器创建并为 ETag 实现动作过滤器，并从 mvc 4 模板缓存 HomeController 10 秒。

这是我的属性：

public class EtagFilterAttribute : ActionFilterAttribute
    {
        private DateTime _currentTime = DateTime.Now;

        private string _currentEtag = string.Empty;

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var httpContext = filterContext.RequestContext.HttpContext;

            string eTag = httpContext.Request.Headers["ETag"];

            string responseETag = GetEtag();

            if (!string.IsNullOrEmpty(eTag))
            {
                if (eTag.Equals(responseETag))
                {
                    filterContext.HttpContext.Response.StatusCode = 304;

                    filterContext.HttpContext.Response.StatusDescription = "Not Modified";
                }

                return;
            }

            filterContext.HttpContext.Response.Cache.SetCacheability(HttpCacheability.ServerAndPrivate);

            filterContext.HttpContext.Response.AddHeader("ETag", responseETag);

            filterContext.HttpContext.Response.Cache.SetETag(responseETag);
        }

        private string GetEtag()
        {
            if (_currentTime <= DateTime.Now.AddSeconds(10))
            {
                return _currentEtag;
            }

            _currentEtag = GenerateEtag();

            return _currentEtag;
        }

        private string GenerateEtag()
        {
            return Guid.NewGuid().ToString().Substring(0, 20);
        }
    }

这是 HomeController：

public class HomeController : Controller
    {
        [EtagFilter]
        public ActionResult Index()
        {
            ViewBag.Message = "Modify this template to jump-start your ASP.NET MVC application.";

            return View();
        }

        [EtagFilter]
        public ActionResult About()
        {
            ViewBag.Message = "Your app description page.";

            return View();
        }

        [EtagFilter]
        public ActionResult Contact()
        {
            ViewBag.Message = "Your contact page.";

            return View();
        }
    }

它已编译并运行，但在 Chrome 开发者工具 Network->Headers 选项卡中我没有看到 ETag：

请求地址：http://:1772/Home/关于请求方式：GET 状态码：200 OK 请求头查看源接受：text/html,application/xhtml+xml,application/xml;q=0.9, /;q=0.8 Accept-Encoding:gzip,deflate,sdch Accept-Language:en-US,en;q=0.8 Connection:keep-alive Cookie:__RequestVerificationToken=q0yQrf5ee5bsOW-1OXKK754FeRZM89uNQQ1rvN2cVRXaHsPGhOTt2zw2cUyfmu-0uZGLL5-ebs-iJH1-RQ3Q7qb6z4jTHNY8yGJQ3KBYhRs1 Host:localhost: 1772 Referer:http://:1772/ User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/29.0.1547.76 Safari/537.36 Response Headersview source Cache-Control:private Content -编码：gzip 内容长度：956 内容类型：文本/html；charset=utf-8 日期：2013 年 10 月 4 日星期五 15:34:02 GMT 服务器：Microsoft-IIS/8.0 Vary:Accept-Encoding X-AspNet-Version:4.0.30319 X-AspNetMvc-Version:4.0 X-Powered- By:ASP.NET X-SourceFiles:=?UTF-8?B?ZDpcTXlEb2N1bWVudHNcR2VuZXJhbFxDI1wuTmV0IE1lbnRvc​​mluZyBQcm9ncmFtXEhUVFBcRXhhbXBsZVxIdHRwRm9yRGV2ZWxvcGVyc1xIb21lXEFib3V0?=

你能告诉我我哪里错了吗？

Answer 1

这有效：

public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var httpContext = filterContext.RequestContext.HttpContext;

            string eTag = httpContext.Request.Headers["ETag"];

            string responseETag = GetEtag();

            if (!string.IsNullOrEmpty(eTag))
            {
                if (eTag.Equals(responseETag))
                {
                    filterContext.HttpContext.Response.StatusCode = 304;

                    filterContext.HttpContext.Response.StatusDescription = "Not Modified";
                }

                return;
            }

            httpContext.Response.AddHeader("ETag", responseETag);
        }