I quickly through this sample together because someone in the newsgroups wanted a way to create a filesystem view through the ASP.Net TreeView control. Note: I'm not touching this with icons or any other niceness, that's an exercise left to the reader:

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs" Inherits="WebUserControl" %>
<script runat="server" language="C#">
    protected void Page_Load(object sender, EventArgs e)
    {
        System.IO.DirectoryInfo di =
            new System.IO.DirectoryInfo(@"c:\mydirectory\mydirectoryschild\");
        TreeNode root = new TreeNode(di.Name);
        this.TreeView1.Nodes.Add(root);
        HydrateTree(di, root);
    }

    private void HydrateTree(System.IO.DirectoryInfo dir, TreeNode parent)
    {
        foreach (System.IO.FileInfo file in dir.GetFiles())
        {
            parent.ChildNodes.Add(new TreeNode(file.Name));
        }
        foreach (System.IO.DirectoryInfo di in dir.GetDirectories())
        {
            TreeNode child = new TreeNode(di.Name);
            parent.ChildNodes.Add(child);
            HydrateTree(di, child);
        }
        return;
    }
</script>
<asp:TreeView ID="TreeView1" runat="server">
</asp:TreeView>

This is what it looks like on my machine:

Recommended reading: