I use a TreeView to display a sitemap, but I wanted next to every link a small image; when clicked, it would add the link to a list of favorites in the Profile of the site user.

So I made a custom TreeNode, but I cannot figure out how to make the image postback to the page and expose an event that I can capture and use to add the link to the Profile.

Looked around here and via google, but somehow no one ever seems to have done this. Can anyone help out?

Solved it myself by thinking about it in a different light: I now generate the links to the pages in RenderPreText, and I add a TreeNodeSelectAction.Select to each custom TreeNode -- I also set the ImageUrl of the TreeNode and when a user clicks on that, I can access the event and do what I need to do.

Mind you, I'm a bit baffled that it is so hard to do all this via the TreeView.

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

namespace MySite
{
	public class MyTreeView : TreeView
	{
        protected override TreeNode CreateNode()
        {
            return new MyTreeNode();
        }
	}
}

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

namespace MySite
{
    public class MyTreeNode : TreeNode
    {
        private string NodeText = string.Empty;
        private string NodeURL = string.Empty;

        public MyTreeNode()
        {
        }

        public MyTreeNode(string aText)
        {
            NodeText = aText;
        }

        public MyTreeNode(string aText, string aNavigateUrl,bool IsFavorite)
        {
            NodeText = aText;
            NodeURL = aNavigateUrl;

            if (NodeURL != null && NodeURL != string.Empty && NodeURL != "#")
            {
                if (IsFavorite)
                {
                    this.ImageUrl = "~/Images/Remove.gif";
                    this.ImageToolTip = "remove from favorites";
                }
                else
                {
                    this.ImageUrl = "~/Images/Add.gif";
                    this.ImageToolTip = "add to favorites";

                }
            }
            this.Text = string.Empty;
            this.Value = NodeURL;
            this.SelectAction = TreeNodeSelectAction.Select;
        }

        protected override void RenderPreText(HtmlTextWriter writer)
        {
            bool bShowlink = false;
            if (NodeURL != null && NodeURL != string.Empty && NodeURL != "#")
            {
                bShowlink = true;
            }
            // start span
            writer.AddAttribute("class", "FavoriteURL");
            writer.RenderBeginTag((HtmlTextWriterTag.Span));
            if (bShowlink)
            {
                // start link
                writer.AddAttribute("href", NodeURL);
                writer.AddAttribute("title", "go to page");
                writer.RenderBeginTag(HtmlTextWriterTag.A);
            }
            // write text
            writer.Write(NodeText);
            if (bShowlink)
            {
                // finish link
                writer.RenderEndTag();
            }
            // finish span
            writer.RenderEndTag();

            base.RenderPreText(writer);
        }

        protected override object SaveViewState()
        {
            object[] arrState = new object[3];
            arrState[0] = base.SaveViewState();
            arrState[1] = this.NodeText;
            arrState[2] = this.NodeURL;

            return arrState;
        }

        protected override void LoadViewState(object savedState)
        {
            if (savedState != null)
            {
                object[] arrState = savedState as object[];

                this.NodeText = (string)arrState[1];
                this.NodeURL = (string)arrState[2];
                base.LoadViewState(arrState[0]);
            }
        }
    }
}

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the .aspx page (this is just the relevant code, not the complete page):

<%@ Register Assembly="MySite" Namespace="MySite" TagPrefix="My" %>

<My:MyTreeView ID="tvNavigation" runat="server" OnSelectedNodeChanged="Node_Selected" />
 

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namespace MySite
{
    public partial class Explore : Page
    {
        private Hashtable htFavorites = new Hashtable();

        protected void Page_Load(object sender, EventArgs e)
        {
            foreach (string sURL in Profile.Favorites)
            {
                htFavorites.Add(sURL, true);
            }
            if (!IsPostBack)
            {
                FillTree();
            }
        }

        protected void Node_Selected(object sender, EventArgs e)
        {
            MyTreeView oSTV = (MyTreeView)sender;
            string sSelectedURL = oSTV.SelectedNode.Value;
            if (htFavorites[sSelectedURL] != null)
            {
                Profile.Favorites.Remove(sSelectedURL);
                htFavorites.Remove(sSelectedURL);
            }
            else
            {
                Profile.Favorites.Add(sSelectedURL);
                htFavorites.Add(sSelectedURL, true);
            }
            FillTree();
        }
        
        private void FillTree()
        {
            // needed because we rebuild the tree each time
            tvNavigation.Nodes.Clear();
            
            // ...code to add nodes to the tree...

            tvNavigation.ExpandAll();
        }
    }
}