Here is the part of the code I used for creating a multi level custom tree. I hope it helps.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Web;

using Project.BLL.Default;
using Project.BLL.Utilities;
using Project.DAL.CollectionClasses;
using Project.DAL.EntityClasses;
using Project.General.Default;
using Project.Presentation.Layer;
using Project.WebApplication.Sections.Products.Category;
using Project.WebApplication.Sections.Products.Product;
using umbraco.cms.presentation.Trees;
using umbraco.interfaces;
using umbraco.IO;

namespace Project.WebApplication.Sections.Articles
{
    public class LoadProductsTree : BaseTree
    {
        private ControllerLayer _controllerLayer;

        #region Properties

        public ControllerLayer ControllerLayer
        {
            get
            {
                if (_controllerLayer == null)
                {
                    _controllerLayer = new ControllerLayer();
                }
                return _controllerLayer;
            }
        }

        #endregion

        public LoadProductsTree(string application)
            : base(application)
        {
        }

        protected override void CreateRootNodeActions(ref List<IAction> actions)
        {
            //Remove the default actions.
            actions.Clear();
        }

        protected override void CreateAllowedActions(ref List<IAction> actions)
        {
            //Remove the default actions.
            actions.Clear();
        }

        protected override void CreateRootNode(ref XmlTreeNode rootNode)
        {
            //Create the root node.
            rootNode.Icon = "database_table.png";
            rootNode.OpenIcon = "database_table.png";
            rootNode.NodeType = TreeAlias;
            rootNode.Text = "Categories";
            rootNode.NodeID = Constants.ROOTPATH;
            rootNode.Menu.Add(CreateCategoryAction.Instance);
            rootNode.Menu.Add(SortCategoryAction.Instance);
        }

        public override void Render(ref XmlTree tree)
        {
            //Check if the current tree is a product.
            string isProduct = HttpContext.Current.Request.QueryString["isProduct"];

            if (string.IsNullOrEmpty(isProduct))
            {
                //Get all the categories which will be displayed.
                CategoryCollection categoryCollection = ControllerLayer.GetCategories();

                foreach (CategoryEntity categoryEntity in categoryCollection)
                {
                    //Create the category node.
                    XmlTreeNode xNode = XmlTreeNode.Create(this);
                    xNode.NodeID = categoryEntity.CategoryId.ToString();
                    xNode.Text = categoryEntity.BackendName;
                    xNode.Action = string.Format("javascript:openCategoryDetails('{0}');", categoryEntity.CategoryId);
                    xNode.Icon = "table_multiple.png";
                    xNode.OpenIcon = "table_multiple.png";
                    xNode.Menu.Add(CreateProductAction.Instance);
                    xNode.Menu.Add(DeleteCategoryAction.Instance);
                    xNode.Menu.Add(SortProductAction.Instance);
                    if (ControllerLayer.HasProducts(categoryEntity.CategoryId))
                    {
                        //If the node has children show them.
                        xNode.HasChildren = true;
                        xNode.Source = string.Format(IOHelper.ResolveUrl(SystemDirectories.Umbraco) + "/tree.aspx?rnd={0}&id={1}&treeType={2}&contextMenu={3}&isDialog={4}&isProduct=true", Guid.NewGuid(), categoryEntity.CategoryId, TreeAlias, ShowContextMenu, IsDialog);
                    }

                    tree.treeCollection.Add(xNode);
                }
            }
            else if (isProduct == "true")
            {
                //Get the id of the category.
                int categoryId = this.id;

                //Get all the products which will be displayed.
                ProductCollection productCollection = ControllerLayer.GetProducts(categoryId);

                foreach (ProductEntity productEntity in productCollection)
                {
                    //Create the product node.
                    XmlTreeNode xNode = XmlTreeNode.Create(this);
                    xNode.NodeID = productEntity.ProductId.ToString();
                    xNode.Text = productEntity.BackendName;
                    xNode.Action = string.Format("javascript:openProductDetails('{0}');", productEntity.ProductId);
                    xNode.Icon = "table_gear.png";
                    xNode.OpenIcon = "table_gear.png";
                    xNode.Menu.Add(DeleteProductAction.Instance);
                    tree.treeCollection.Add(xNode);
                }
            }
        }

        public override void RenderJS(ref StringBuilder Javascript)
        {
            //Opens the category details page.
            Javascript.Append(
                                @"
                        function openCategoryDetails(id) {
                            parent.right.document.location.href = '" + IOHelper.ResolveUrl(SystemDirectories.Umbraco) + @"/customSections/products/CategoryDetails.aspx?id=' + id;
                        }
                        ");

            //Opens the product details page.
            Javascript.Append(
                                @"
                        function openProductDetails(id) {
                            parent.right.document.location.href = '" + IOHelper.ResolveUrl(SystemDirectories.Umbraco) + @"/customSections/products/ProductDetails.aspx?id=' + id;
                        }
                        ");
        }
    }
}

Jeroen

Hi Jeroen,
Thanks for your response.

Is the main part for rendering children this:

Yes xNode.Source is used to render children. When you try to open a child node "public override void Render(ref XmlTree tree)" is called again, but with different values. That's why I add "&isProduct=true" to the querystring and "&id={1}" is the id of the parent. It's a bit of a custom way and there are better ways to do it. This blog might help: http://www.robertgray.net.au/2011/5/27/creating-custom-multi-level-trees-in-umbraco.aspx

Jeroen

Hi Jeroen,
Thanks for that! Seems like it should do the trick. Im away from my computer for a few days then will give it a try!

Cheers, 

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