Returns the root System.Web.SiteMapNode of the site map navigation structure.
The XmlSiteMapProvider.BuildSiteMap method is called to load and build the site map from persistent storage.
For the default behavior when security trimming is enabled, see "Remarks" in SiteMapProvider.IsAccessibleToUser(HttpContext, SiteMapNode).
After the System.Web.XmlSiteMapProvider object parses and loads site map data, all loaded System.Web.SiteMapNode objects and System.Web.SiteMapNodeCollection collections are made read-only. When the System.Web.XmlSiteMapProvider parses the SiteMapNode.Url property from a site map file, it converts application-relative URLs, as well as relative URLs, to application-absolute virtual paths.
The System.Web.XmlSiteMapProvider subscribes to file change notifications for the .sitemap file. If any change is made to the .sitemap file, the System.Web.XmlSiteMapProvider is reloaded, and the site map structure is rebuilt.