You could add some logic into the BuildItem method in TreeViewAdapter.cs (or vb).  That file contains the logic that creates the adapted HTML for the TreeView control.  You can find that file in App_Code\Adapters.

Presumably, you would want to test (in BuildItem) to see if a node in the tree conformed to some special condition (like it corresponded to the active page) and then add another class to its class attribute value.  Remember that you can have multiple classes listed in the class attribute by separating them with spaces.

The only problem with that approach is that it tends to make the TreeView adapter "know" things that ideally it shouldn't have to know about -- like that your site likes to style nodes in the tree specially when they correspond to the active page.  Still, it may be the best approach for you in this case.

If you wanted to get a little more fancy you could add an expando property to the TreeView control, something like (MarkActive).  The adapter could look for that expando property on the control and use its value to figure out if particular nodes should be marked (using an extra CSS class) as being "active."

Expando properties are simply extra (custom) properties that you add to any ASP.NET control.  The kit uses an expando property called CssSelectorClass.  So, you can follow its usage logic to see how you might add your own expando, MarkActive.

If you get stuck, post something here.  Maybe others in the community can help you figure this out, too.

-Russ-

<siteMapNode title="Billing" url="~/billing/default.aspx">
	<siteMapNode title="Setup" url="~/billing/setup">
		<siteMapNode url="~/billing/listbillmessages.aspx"	title="List Enabled Bill Messages"/>
		<siteMapNode url="~/billing/newbillmessage.aspx"	title="Add a new Bill Message"/>

using System;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace CSSFriendly
{
    public class TreeViewAdapter : System.Web.UI.WebControls.Adapters.HierarchicalDataBoundControlAdapter
    {
        public TreeNode activeNode;
        public bool isActivePath = false;

        public TreeViewAdapter()
        {
            //
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            RegisterScripts();
        }

        private void RegisterScripts()
        {
            Utility.RegisterScripts(Page);
            Page.ClientScript.RegisterClientScriptInclude(GetType(), GetType().ToString(), Page.ResolveUrl("~/includes/adapters/treeview.js"));
        }

        protected override void RenderBeginTag(HtmlTextWriter writer)
        {
            if ((Control != null) && (Control.Attributes["CssSelectorClass"] != null) && (Control.Attributes["CssSelectorClass"].Length > 0))
            {
                writer.WriteLine();
                writer.WriteBeginTag("div");
                writer.WriteAttribute("class", Control.Attributes["CssSelectorClass"]);
                writer.Write(HtmlTextWriter.TagRightChar);
                writer.Indent++;
            }

            writer.WriteLine();
            writer.WriteBeginTag("div");
            writer.WriteAttribute("class", Control.Attributes["CssSelectorClass"] + "-inside");
            writer.Write(HtmlTextWriter.TagRightChar);
        }

        protected override void RenderEndTag(HtmlTextWriter writer)
        {
            writer.WriteEndTag("div");

            if ((Control != null) && (Control.Attributes["CssSelectorClass"] != null) && (Control.Attributes["CssSelectorClass"].Length > 0))
            {
                writer.Indent--;
                writer.WriteLine();
                writer.WriteEndTag("div");
            }

            writer.WriteLine();
        }

        protected override void RenderContents(HtmlTextWriter writer)
        {
            TreeView treeView = Control as TreeView;
            if (treeView != null)
            {
                AssureAllNodesAreBuilt(treeView);
                activeNode = treeView.SelectedNode;

                writer.Indent++;
                BuildItems(treeView.Nodes, true, true, writer);
                writer.Indent--;
                writer.WriteLine();
            }
        }

        private void BuildItems(TreeNodeCollection items, bool isRoot, bool isExpanded, HtmlTextWriter writer)
        {
            if (items.Count > 0)
            {
                writer.WriteLine();

                writer.WriteBeginTag("ol");
                if (!isExpanded)
                {
                    writer.WriteAttribute("class", "menu-hide");
                }
                writer.Write(HtmlTextWriter.TagRightChar);
                writer.Indent++;

                foreach (TreeNode item in items)
                {
                    BuildItem(item, writer);
                }

                writer.Indent--;
                writer.WriteLine();
                writer.WriteEndTag("ol");
            }
        }

        private void BuildItem(TreeNode item, HtmlTextWriter writer)
        {
            TreeView treeView = Control as TreeView;
            if ((treeView != null) && (item != null) && (writer != null))
            {
                isActivePath = false;
                if (IsActivePath(item)) // cj
                    item.Expand();

                #region [start tags]
                writer.WriteLine();
                writer.WriteBeginTag("li");

                writer.WriteAttribute("class", GetNodeClass(item, isActivePath)); // cj
                writer.Write(HtmlTextWriter.TagRightChar);
                writer.Indent++;
                writer.WriteLine();
                #endregion

                #region [expand button]
                if (item.ChildNodes.Count > 0)
                {
                    writer.WriteBeginTag("span");
                    writer.WriteAttribute("class", ((item.Expanded == true) ? "menu-collapse" : "menu-expand"));
                    writer.WriteAttribute("onclick", "ExpandCollapse__AspNetTreeView(this)");
                    writer.Write(HtmlTextWriter.TagRightChar);
                    writer.Write(" ");
                    writer.WriteEndTag("span");
                    writer.WriteLine();
                }
                #endregion

                if (item.NavigateUrl.Length > 0)
                {
                    #region [create link]
                    writer.WriteBeginTag("a");
                    if (item.Parent == null)
                        writer.WriteAttribute("class", "chapter");

                    writer.WriteAttribute("href", Page.ResolveUrl(item.NavigateUrl));
                    if (item.Target.Length > 0)
                    {
                        writer.WriteAttribute("target", item.Target);
                    }
                    if (item.ToolTip.Length > 0)
                    {
                        writer.WriteAttribute("title", item.ToolTip);
                    }
                    else if (treeView.ToolTip.Length > 0)
                    {
                        writer.WriteAttribute("title", treeView.ToolTip);
                    }
                    writer.Write(HtmlTextWriter.TagRightChar);
                    writer.Indent++;
                    writer.WriteLine();
                    #endregion
                }
                else
                {
                    #region [parent - no link]
                    writer.WriteBeginTag("span");
                    if (item.ChildNodes.Count > 0)
                    {
                        writer.WriteAttribute("class", "menu-clickable");
                        writer.WriteAttribute("onclick", "ExpandCollapse__AspNetTreeView(this.parentNode.getElementsByTagName('span')[0])");
                    }
                    else
                    {
                        writer.WriteAttribute("class", "menu-nothing");
                    }
                    writer.Write(HtmlTextWriter.TagRightChar);
                    writer.Indent++;
                    writer.WriteLine();
                    #endregion
                }

                #region [set child graphic]
                string imgSrc = GetImageSrc(treeView, item);
                if (imgSrc.Length > 0)
                {
                    writer.WriteBeginTag("img");
                    writer.WriteAttribute("src", Page.ResolveUrl(imgSrc));
                    writer.WriteAttribute("alt", item.ToolTip.Length > 0 ? item.ToolTip : (treeView.ToolTip.Length > 0 ? treeView.ToolTip : item.Text));
                    writer.Write(HtmlTextWriter.SelfClosingTagEnd);
                }
                #endregion

                writer.Write(item.Text);

                #region [end tags and insert children]
                if (item.NavigateUrl.Length > 0)
                {
                    writer.Indent--;
                    writer.WriteLine();
                    writer.WriteEndTag("a");
                }
                else
                {
                    writer.Indent--;
                    writer.WriteLine();
                    writer.WriteEndTag("span");
                }

                if ((item.ChildNodes != null) && (item.ChildNodes.Count > 0))
                {
                    BuildItems(item.ChildNodes, false, (item.Expanded == true), writer);
                }

                writer.Indent--;
                writer.WriteLine();
                writer.WriteEndTag("li");
                #endregion
            }
        }

        private string GetNodeClass(TreeNode item, bool isActive)
        {
            string value = Control.Attributes["CssSelectorClass"] + "-leaf";

            if (item != null)
            {
                if (item.Depth == 0)
                {
                    if (item.ChildNodes.Count > 0)
                    {
                        value = Control.Attributes["CssSelectorClass"] + "-root " + Control.Attributes["CssSelectorClass"] + "-parent";
                    }
                    else
                    {
                        value = Control.Attributes["CssSelectorClass"] + "-root " + Control.Attributes["CssSelectorClass"] + "-leaf";
                    }
                }
                else if (item.ChildNodes.Count > 0)
                {
                    value = Control.Attributes["CssSelectorClass"] + "-parent";
                }
            }

            if (isActive) // cj
            {
                TreeView treeView = Control as TreeView;  // find me - this is kind of redundant
                value = treeView.SelectedNodeStyle.CssClass + " " + value;
            }

            return value;
        }

        private string GetImageSrc(TreeView treeView, TreeNode item)
        {
            string imgSrc = "";

            if ((treeView != null) && (item != null))
            {
                imgSrc = item.ImageUrl;

                if (imgSrc.Length == 0)
                {
                    if (item.Depth == 0)
                    {
                        if ((treeView.RootNodeStyle != null) && (treeView.RootNodeStyle.ImageUrl.Length > 0))
                        {
                            imgSrc = treeView.RootNodeStyle.ImageUrl;
                        }
                    }
                    else
                    {
                        if (item.ChildNodes.Count == 0)
                        {
                            if ((treeView.LeafNodeStyle != null) && (treeView.LeafNodeStyle.ImageUrl.Length > 0))
                            {
                                imgSrc = treeView.LeafNodeStyle.ImageUrl;
                            }
                        }
                        else if ((treeView.ParentNodeStyle != null) && (treeView.ParentNodeStyle.ImageUrl.Length > 0))
                        {
                            imgSrc = treeView.ParentNodeStyle.ImageUrl;
                        }
                    }
                }

                if ((imgSrc.Length == 0) && (treeView.LevelStyles != null) && (treeView.LevelStyles.Count > item.Depth))
                {
                    if (treeView.LevelStyles[item.Depth].ImageUrl.Length > 0)
                    {
                        imgSrc = treeView.LevelStyles[item.Depth].ImageUrl;
                    }
                }
            }

            return imgSrc;
        }

        private void AssureAllNodesAreBuilt(TreeView treeView)
        {
            if (treeView != null)
            {
                int currentDepth = treeView.ExpandDepth;
                treeView.ExpandDepth = -1;
                treeView.ExpandAll();
                treeView.ExpandDepth = currentDepth;
                if (treeView.ExpandDepth > -1)
                {
                    treeView.CollapseAll();
                    ExpandToDepth(treeView.Nodes, treeView.ExpandDepth);
                }
            }
        }

        static public void ExpandToDepth(TreeNodeCollection nodes, int expandDepth)
        {
            foreach (TreeNode node in nodes)
            {
                if (node.Depth < expandDepth)
                {
                    node.Expand();
                    ExpandToDepth(node.ChildNodes, expandDepth);
                }
            }
        }

        public bool IsActivePath(TreeNode node) // cj
        {
            foreach (TreeNode child in node.ChildNodes)
            {
                IsActivePath(child);
            }

            if (node.Equals(activeNode))
                isActivePath = true;

            return isActivePath;
        }
    }
}