Listing tree-like structure based on parent

I have an XML Sitemap like this

<?xml version="1.0" encoding="utf-8" ?>
<Menu>
    <MenuItem Name="Page 1" Url="~/page1.aspx">
        <MenuItem Name="SubPage 1" Url="~/subpage1.aspx" />
    </MenuItem>
    <MenuItem Name="Page 2" Url="~/page2.aspx">
        <MenuItem Name="SubPage 1" Url="~/subpage1.aspx" />
        <MenuItem Name="SubPage 2" Url="~/subpage2.aspx">
            <MenuItem Name="ThirdLevel 1" Url="~/thirdlevel1.aspx" />
            <MenuItem Name="ThirdLevel 2" Url="~/thirdlevel2.aspx" />
            <MenuItem Name="ThirdLevel 3" Url="~/thirdlevel3.aspx" />
        </MenuItem>
        <MenuItem Name="SubPage 3" Url="~/subpage3.aspx" />
    </MenuItem>
    <MenuItem Name="Page 3" Url="~/page3.aspx" />
</Menu>

And a recusive function to loop all this out to an <ul> menu like this:

// ^^^ loaded all into an XmlNodeList
private void CreateMenuItems(HtmlTextWriter writer, XmlNodeList menuitems)
{
    writer.RenderBeginTag(HtmlTextWriterTag.Ul);
    foreach (XmlNode item in menuitems)
    {
            writer.RenderBeginTag(HtmlTextWriterTag.Li);
            writer.AddAttribute(HtmlTextWriterAttribute.Href, this.ResolveUrl(item.Attributes["Url"].Value));
            writer.RenderBeginTag(HtmlTextWriterTag.A);
            writer.Write(item.Attributes["Name"].Value);
            writer.RenderEndTag();
            if (item.HasChildNodes)
            {
                // Recusive funktion
                CreateMenuItems(writer, item.ChildNodes);
            }
            writer.RenderEndTag();
    }
    writer.RenderEndTag();
}

All this works very fine and it lists all in a tree-menu like structure.

This is good when I want to create an DropDown menu. But since I want the subpages in a sidebar I need to make a new web control that lists the current page structure based on the upper parent.

So if I am on "Page 2" I want an control to get the items in "Page 2"-ChildNodes. And if I click the "SubPage 2" I want it to list all from the upper parent "Page 2" like:

Page 1
Page 2 *click*
------开发者_StackOverflow社区------ SUB MENU I WANT TO LIST -------------
 --> SubPage 1
 --> SubPage 2 *click*
    --> ThirdLevel 1
    --> ThirdLevel 2
    --> Third Level 3 *current page*
  --> SubPage 3
------------ SUB MENU I WANT TO LIST -------------
Page 3

I am aware I need to detect the current url, finding the XmlNode and go back. But I am unsure how to navigate on that level. :-/

Have you considered using the built in sitemap functionality? FindSiteMapNodeFromKey

No sense handling a bunch of xml if you don't have to.