The System.Web.SiteMapProvider implementation returns null in all cases. Classes that derive from the System.Web.SiteMapProvider class can override the SiteMapProvider.FindSiteMapNodeFromKey(string) method to provide lookup functionality based on a unique key (instead of a URL, which is used by the erload:System.Web.SiteMapProvider.FindSiteMapNode method). Implement the SiteMapProvider.FindSiteMapNodeFromKey(string) method if your site map provider implementation uses the SiteMapNode.Key property of a System.Web.SiteMapNode object as a primary identifier in a site map structure.

The System.Web.StaticSiteMapProvider class provides an implementation that handles searching for site map nodes that do not define a URL.

The System.Web.XmlSiteMapProvider class, which is the default site map provider for ASP.NET, uses the URL of a System.Web.SiteMapNode as a key in the various collections that the classes maintain. Therefore, if a node provides a URL, it must be unique within the scope of the site map provider. If no URL is provided, a unique identifier is generated to identify the System.Web.SiteMapNode.