Removes all elements in the collections of child and parent site map nodes and site map providers that the System.Web.XmlSiteMapProvider object internally tracks as part of its state.
The System.Web.XmlSiteMapProvider class overrides the inherited XmlSiteMapProvider.Clear method to provide additional state cleanup beyond the basic StaticSiteMapProvider.Clear implementation, including clearing its child provider tracking and the XmlSiteMapProvider.RootNode property tracking mechanisms.