protected void Application_BeginRequest()
        {
            HttpResponse Response = HttpContext.Current.Response;
            //获取当前请求的url
            string url = HttpContext.Current.Request.Path;
            //获取请求的文件后缀名
            string extension = Path.GetExtension(url);
            //由于MVC动态页面不带后缀，所有其他有后缀的都加上缓存
            if (!string.IsNullOrWhiteSpace(extension))
            {
                Response.Cache.SetCacheability(HttpCacheability.Public);
                Response.Cache.SetMaxAge(new TimeSpan(8760, 0, 0));
                Response.Headers.Remove("Cache-Control");
                Response.AddHeader("Cache-Control", "public,max-age=31536000");
                Response.Headers.Remove("Expires");
                Response.AddHeader("Expires", DateTime.UtcNow.AddYears(1).ToUniversalTime().ToString("r"));
            }
        }