// The LoadSiteMapData() method loads site navigation
// data from persistent storage into a DataTable.
DataTable siteMap = LoadSiteMapData();

// Create a SiteMapNodeCollection.
SiteMapNodeCollection nodes = new SiteMapNodeCollection();

// Create a SiteMapNode and add it to the collection.
SiteMapNode tempNode;
DataRow row;
int index = 0;

while (index < siteMap.Rows.Count)
{

    row = siteMap.Rows[index];

    // Create a node based on the data in the DataRow.
    tempNode = new SiteMapNode(SiteMap.Provider,
                                row["Key"].ToString(),
                                row["Url"].ToString());

    // Add the node to the collection.
    nodes.Add(tempNode);
    ++index;
}

protected virtual void LoadSiteMapFromStore()
{
  string pathToOpen;

  lock (this)
  {
    // If a root node exists, LoadSiteMapFromStore has already
    // been called, and the method can return.
    if (rootNode != null)
    {
      return;
    }
    else
    {
      pathToOpen = HttpContext.Current.Server.MapPath("~" + "\\" + sourceFilename);

      if (File.Exists(pathToOpen))
      {
        // Open the file to read from.
        using (StreamReader sr = File.OpenText(pathToOpen))
        {

          // Clear the state of the collections and rootNode
          rootNode = null;
          siteMapNodes.Clear();
          childParentRelationship.Clear();

          // Parse the file and build the site map
          string s = "";
          string[] nodeValues = null;
          SiteMapNode temp = null;

          while ((s = sr.ReadLine()) != null)
          {

            // Build the various SiteMapNode objects and add
            // them to the ArrayList collections. The format used
            // is: URL,TITLE,DESCRIPTION,PARENTURL

            nodeValues = s.Split(',');

            temp = new SiteMapNode(this,
                HttpRuntime.AppDomainAppVirtualPath + "/" + nodeValues[0],
                HttpRuntime.AppDomainAppVirtualPath + "/" + nodeValues[0],
                nodeValues[1],
                nodeValues[2]);

            // Is this a root node yet?
            if (null == rootNode &&
                string.IsNullOrEmpty(nodeValues[3]))
            {
              rootNode = temp;
            }

          // If not the root node, add the node to the various collections.
            else
            {
              siteMapNodes.Add(new DictionaryEntry(temp.Url, temp));
              // The parent node has already been added to the collection.
              SiteMapNode parentNode =
                       FindSiteMapNode(HttpRuntime.AppDomainAppVirtualPath + "/" + nodeValues[3]);
              if (parentNode != null)
              {
                childParentRelationship.Add(new DictionaryEntry(temp.Url, parentNode));
              }
              else
              {
                throw new Exception("Parent node not found for current node.");
              }
            }
          }
        }
      }
      else
      {
        throw new Exception("File not found");
      }
    }
  }
  return;
}