MVC 5 捆绑和 Azure CDN（查询字符串）

Question

我一直在关注这个教程：https://azure.microsoft.com/en-us/documentation/articles/cdn-serve-content-from-cdn-in-your-web-application/

一切都很好，直到我注意到捆绑的脚本和 CSS 文件返回 cache: no-cache、expires: -1 和 pragma: no-cache 标头。 当然，这与 Azure 无关。为了证明这一点，我通过直接从我的站点而不是 CDN 访问它们来测试捆绑包 - 即。 mysite.com/bundles/mybundle?v={myassemblyversion}。结果是一样的。当我禁用 CDN，并使用 MVC 生成的 v 查询字符串访问捆绑文件时，标题如预期：公共缓存，到期时间为一年。

我尝试实现IBundleTransform 接口，但context.BundleVirtualPath 是只读的（即使它说获取或设置虚拟路径...）。我也尝试修改Application_EndRequest() 处的响应标头，但也没有用。我最后的赌注是编写 IIS 出站规则，但由于我的包（与“自定义”v 查询字符串一起使用）不返回 Last-Modified 标头，所以这也是徒劳的尝试。

我的问题是：如果我希望我的捆绑文件缓存在客户端上，我该如何使用 MVC 捆绑与 Azure CDN - 也就是说，直到v 查询字符串发生变化？

Answer 1

我知道我玩游戏有点晚了，但我确实找到了解决方法。我正在使用 Frison B Alexander here 的代码。

问题在于，一旦您为 StyleBundle 或 ScriptBundle 重写查询字符串，一年的默认缓存行为将重置为无缓存。这可以通过为每个包重新生成完全相同的查询字符串来解决，MVC 框架在指定每个包的 CDNPath 时使用该查询字符串。

以下是使用 MVC Web 应用模板的方法。这是 BundleConfig 类：

public class BundleConfig
    {
        public static void RegisterBundles(BundleCollection bundles)
        {            
            //we have to go ahead and add our Bundles as if there is no CDN involved.
            //this is because the bundle has to already exist in the BundleCollection
            //in order to get the hash that the MVC framework will generate for the
            //querystring. 
            Bundle jsBundle = new ScriptBundle("~/scripts/js3").Include(
                 "~/Scripts/jquery-{version}.js",
                 "~/Scripts/modernizr-*",
                 "~/Scripts/bootstrap.js",
                 "~/Scripts/respond.js");
            bundles.Add(jsBundle);

            Bundle cssBundle = new StyleBundle("~/content/css3").Include(
                      "~/Content/bootstrap.css",
                      "~/Content/site.css");
            bundles.Add(cssBundle);

#if Debug
            bundles.UseCdn = false; 
#else
            bundles.UseCdn = true;
            //grab our base CDN hostname from web.config...
            string cdnHost = ConfigurationManager.AppSettings["CDNHostName"];

            //get the hashes that the MVC framework will use per bundle for 
            //the querystring. 
            string jsHash = GetBundleHash(bundles, "~/scripts/js3");
            string cssHash = GetBundleHash(bundles, "~/content/css3");

            //set up our querystring per bundle for the CDN path. 
            jsBundle.CdnPath = cdnHost + "/scripts/js3?v=" + jsHash;
            cssBundle.CdnPath = cdnHost + "/content/css3?v=" + cssHash;
#endif
        }

        //Frison B Alexander's code:
        private static string GetBundleHash(BundleCollection bundles, string bundlePath)
        {

            //Need the context to generate response
            var bundleContext = new BundleContext(new HttpContextWrapper(HttpContext.Current), BundleTable.Bundles, bundlePath);

            //Bundle class has the method we need to get a BundleResponse
            Bundle bundle = BundleTable.Bundles.GetBundleFor(bundlePath);
            var bundleResponse = bundle.GenerateBundleResponse(bundleContext);

            //BundleResponse has the method we need to call, but its marked as
            //internal and therefor is not available for public consumption.
            //To bypass this, reflect on it and manually invoke the method
            var bundleReflection = bundleResponse.GetType();

            var method = bundleReflection.GetMethod("GetContentHashCode", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);

            //contentHash is whats appended to your url (url?###-###...)
            var contentHash = method.Invoke(bundleResponse, null);
            return contentHash.ToString(); 
        }
    }