关于MVC RouteExistingFiles疑问后续

前两天写了《关于MVC RouteExistingFiles疑问》，本来希望寻求大佬快速解答，奈何无人问津。

只能查看.NET 源代码，可以使用反编译工具（我用IL spy），也可以在线查看微软提供的：https://referencesource.microsoft.com/
MVC的路由会走UrlRoutingModule，代码在 System.Web/Routing/UrlRoutingModule.cs 中

RouteData routeData = RouteCollection.GetRouteData(context);

GetRouteData的源代码：

 public RouteData GetRouteData(HttpContextBase httpContext) {
            if (httpContext == null) {
                throw new ArgumentNullException("httpContext");
            }
            if (httpContext.Request == null) {
                throw new ArgumentException(SR.GetString(SR.RouteTable_ContextMissingRequest), "httpContext");
            }

            // Optimize performance when the route collection is empty.  The main improvement is that we avoid taking
            // a read lock when the collection is empty.  Without this check, the UrlRoutingModule causes a 25%-50%
            // regression in HelloWorld RPS due to lock contention.  The UrlRoutingModule is now in the root web.config,
            // so we need to ensure the module is performant, especially when you are not using routing.
            // This check does introduce a slight bug, in that if a writer clears the collection as part of a write
            // transaction, a reader may see the collection when it's empty, which the read lock is supposed to prevent.
            // We will investigate a better fix in Dev10 Beta2.  The Beta1 bug is Dev10 652986.
            if (Count == ) {
                return null;
            }

            bool isRouteToExistingFile = false;
            bool doneRouteCheck = false; // We only want to do the route check once
            if (!RouteExistingFiles) {
                isRouteToExistingFile = IsRouteToExistingFile(httpContext);
                doneRouteCheck = true;
                if (isRouteToExistingFile) {
                    // If we're not routing existing files and the file exists, we stop processing routes
                    return null;
                }
            }

            // Go through all the configured routes and find the first one that returns a match
            using (GetReadLock()) {
                foreach (RouteBase route in this) {
                    RouteData routeData = route.GetRouteData(httpContext);
                    if (routeData != null) {
                        // If we're not routing existing files on this route and the file exists, we also stop processing routes
                        if (!route.RouteExistingFiles) {
                            if (!doneRouteCheck) {
                                isRouteToExistingFile = IsRouteToExistingFile(httpContext);
                                doneRouteCheck = true;
                            }
                            if (isRouteToExistingFile) {
                                return null;
                            }
                        }
                        return routeData;
                    }
                }
            }

            return null;
        }

说实话，没看出来什么。

好吧，依稀记得可以调试源代码，也是查了一下，配置VS，下载PDB文件，就能调试了。具体设置，微软地址：https://referencesource.microsoft.com/setup.html

有类似需求的同学可以参考这篇文章，能详细点：https://blog.csdn.net/egman/article/details/78281424

然而，不知道什么原因，我用的VS2017怎样都无法进入源代码。

于是一个问题就变成了两个问题。

于是又搜其他办法，发现JB的DotPeek软件可以，官方地址：https://www.jetbrains.com/decompiler/

这里就不详细介绍操作了，可以参考园友博客：https://www.cnblogs.com/herenwei-wayne/p/5595429.html

run起来，终于进入到源码中GetRouteData方法中了

依次请求静态资源地址，进行调试：

①/a.jpg：匹配到默认路由“controller/action/id”,controller是a.jpg
②/Theme/a.jpg：匹配到默认路由“controller/action/id”,controller是Theme，Action是a.jpg
③/Areas/Admin/a.jpg：匹配到默认路由“controller/action/id”...
④/Areas/Admin/Theme/a.jpg：未匹配到任何路由，renturn

之前的理解是，

1.配到到路由，比如输入a/b/1，但未找到对应的控制器等，提示不存在

2.未匹配到路由，比如输入a/b/c/d/e/f，也会提示不存在

但事实上，

1.配到到路由，比如输入a/b/1，但未找到对应的控制器等，提示不存在（程序可以捕获）

2.未匹配到路由，比如输入a/b/c/d/e/f，路由中return，交由IIS处理

所以，如果利用此特性做文件夹的访问控制，一定要设置对应文件夹的路由规则，然后处理。