Display an image for a TreeNode

Question

I try to display Images at a node in a Treeview. The Treeview is in an ascx control cause i need it multiple times.

I use the following code:

 <asp:TreeView ID="FolderTree" runat="server"  BackColor="White">
            <NodeStyle ForeColor="Black" ImageUrl="~/App_GlobalResources/folderClosed.png" />
            <ParentNodeStyle ImageUrl="~/App_GlobalResources/folderOpen.png" />
            <RootNodeStyle ImageUrl="~/App_GlobalResources/folderOpen.png" />
        </asp:TreeView>

Thsi code semms to be right for me, and its also displayed right in the designer.

But when i start the page, not a single picture is shown. Only the default collapsebuttons are visible. What am i doing wrong?

Many thanks in advance.

Edit: I added the code how i populate the control

 private void Page_Load(object sender, System.EventArgs e)
    {
        try
        {
            if (!Page.IsPostBack)
            {
                var devData = Foo.GetDevices(); // returns a list with all devices
                    foreach (string temp in devData)
                    {
                        this.FolderTree.Nodes.Add(new TreeNode() { Text = temp, ImageUrl = "~/App_GlobalResources/folderOpen.png" });
                    }
            }
        }
        catch(Exception error)
        {
            //errorhandling
        }
    }

Edit 2: I assume i have that bug: forums.asp.net/t/943367.aspx but the suggested Solution isnt working! (see code above, i already set the value via code. Does anybody know a solution/ a hotfix (to use in an webusercontrol(.ascx))?

I also tried (on my base site):

 protected override void OnSaveStateComplete(EventArgs e)
    {
        foreach (TreeNode tmpNode in this.LeftSelectControl.AccessFolderView.Nodes) //AccessFolderView = var, which contains the treeview of the ascx (to access it)
        {
            tmpNode.ImageUrl = "~/App_GlobalResources/folderOpen.png";
        }
    }

Answer 1

Use the DHTMLX Tree View a Open source javascript library that combines well in C# Fluidly. It will produce nice tree view with images.

Its very simple to use in C# aspx page.

Click Here for Dhtmlx tree

Answer 2

Never done the way you styled your TreeView. But this is how i style my Treeview. Hope it helps you.

<asp:TreeView ID="treeView" runat="server" NodeIndent="20" ExpandDepth="0" NodeStyle-HorizontalPadding="2"
            ShowLines="true" ExpandImageUrl="../images/Open_Folder.png" CollapseImageUrl="../images/Close_Folder.png"
            ForeColor="Black">
</asp:TreeView>

Answer 3

I found a Solution: Dont use App_GlobalResources.

I wont mark this as answer cause this was an stupid mistake by me. You can access App_* Folders only serverside, not clientside.