关于MVC RouteExistingFiles疑问后续

RouteData routeData = RouteCollection.GetRouteData(context);

 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;
        }