<?xml version="1.0" encoding="utf-8"?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0">
  <StyleNodes>
  </StyleNodes>
  <siteMapNode url="~/default.html" name="default">
    <siteMapNodes>
      <siteMapNode name="aboutus" url="~/aboutus.html">
      </siteMapNode>
      <siteMapNode type="custom" name="contactus" url="~/contactus.html">
        <Controls>
          <Control name="ContactUsForm" placeholder="Center">
          </Control>
        </Controls>
      </siteMapNode>
      <siteMapNode type="file" name="sitemap" url="~/sitemap.html">
        <Controls>
          <Control name="SiteMap" placeholder="Center">
          </Control>
        </Controls>
      </siteMapNode>
      ...
  </siteMapNodes>
 </sitemapNode>
 </siteMap>

            modFile.Load(file.FullName);
            XPathNavigator navigator = modFile.CreateNavigator();
            XmlNamespaceManager manager = new XmlNamespaceManager(navigator.NameTable);
            manager.AddNamespace("sm", "http://schemas.microsoft.com/AspNet/SiteMap-File-1.0");
            navigator.MoveToFirstChild();
            XPathNodeIterator nodes = navigator.Select("/sm:siteMapNode", manager);
            if (nodes.MoveNext())
            {
             ...
             }