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 == 0) { ???????????????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。
关于MVC RouteExistingFiles疑问后续
原文地址：https://www.cnblogs.com/talentzemin/p/10326415.html