TreeNodePopulateOnDemand_Files.aspx font size:
<%@ Import namespace="System.IO" %>

<html>
<head>
<title>Populating TreeView Nodes On Demand</title>
<link rel="stylesheet" href="/shared/netdemos.css">

<script language="C#" runat="server">
void populateNode ( Object source, TreeNodeEventArgs e ) {
   TreeNode node = e.Node;
   string fullPath = Request.MapPath ( node.Value, Request.ApplicationPath, false );

   // enumerate directories
   string [ ] dirs = Directory.GetDirectories ( fullPath );
   foreach ( string dir in dirs ) {
      string virtualDir = node.Value.TrimEnd ( '/' ) + "/" + Path.GetFileName ( dir );
      if ( virtualDir.IndexOf ( "admin" ) == -1 || virtualDir.IndexOf ( "tmp" ) == -1 ) {
         TreeNode newNode = new TreeNode ( Path.GetFileName ( dir ), virtualDir );
         if ( Directory.GetFiles ( dir, "*.asp?" ).Length > 0 || Directory.GetDirectories ( dir ).Length > 0 ) {
            newNode.PopulateOnDemand = true;
            node.ChildNodes.Add ( newNode );
         }
      }
   }

   // enumerate files
   string [ ] files = Directory.GetFiles ( fullPath, "*.asp?" );
   foreach ( string file in files ) {
      TreeNode newNode = new TreeNode ( Path.GetFileName ( file ), Path.GetFileName ( file ) );
      newNode.NavigateUrl = "~/" + file.Substring ( Request.PhysicalApplicationPath.Length );
      node.ChildNodes.Add ( newNode );
   }
}
</script>
</head>

<body>
<!-- #include virtual="~/shared/top.inc" -->
<div class="header"><h2>Populating <span class="hilite">TreeView Nodes</span> On Demand</h2></div>

<!-- #include virtual="~/shared/viewsrc_top.inc" -->
<hr size=1 width=92%>

<form runat="server">
   <p align="center">This example demonstrates using the TreeView <i>PopulateOnDemand</i> feature<br>
      to programmatically create <span class="hilite">TreeNodes</span> from the file system of the application that contains this sample. </p>

   <div style="margin-left:50">
   <asp:treeview id="myTreeView" runat="server"
      imageset="XPFileExplorer"
      nodestyle-horizontalpadding=3
      showlines expanddepth=1 target="_ext"
      onTreeNodePopulate="populateNode">

      <nodes>
         <asp:treenode text="asp.net.ph" value="~/" populateondemand />
      </nodes>

   </asp:treeview>
   </div>

</form>

<hr size=1 width=92%>
<!-- #include virtual="~/shared/viewsrc.inc" -->

</body>
</html>