Building a TreeView on Demand Using AJAX

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Xml;
using System.Configuration;

namespace ajaxtree
{
	/// <summary>
	/// Summary description for GetTreeContents.
	/// </summary>
	public class GetTreeContents : System.Web.UI.Page
	{
	 	private void Page_Load(object sender, System.EventArgs e)
		{			
			//id passed thro' the url query string
			string key = Request.QueryString["q"]; 

			if (key != null)
			{
				//read the xml tree file from the web.config file 
				//add the following key in web.config
				//<appSettings>
				//<add key="XmlTree" value="~/TreeSource.XML" />
				String path = Server.MapPath(ConfigurationSettings.AppSettings["XmlTree"]);
			
				//I use XmlDocument object here to manipulate Xml- You can use other objects
				//You can cache the XmlDocument.OuterXml string
				XmlDocument xmlTree = new XmlDocument();
				xmlTree.Load(path);
				System.IO.StringReader xmlSR = new System.IO.StringReader(xmlTree.OuterXml);
			
				//If you want to use database driven tree you skip above codes
				//but the columns should be there in the data table
				DataSet ds = new DataSet();
				ds.ReadXml(xmlSR);
				DataView dv = ds.Tables[0].DefaultView;

				//filter for the parent
				dv.RowFilter = " ParentID = '" + key + "'";

				//render the brower with a <UL> tag and <LI> list
				//I have used some styles
				Response.Write ("<ul class='wTreeStyle'>"); 

				//write all the children here
				for(int i=0; i < dv.Count; i++)
				{	
					//formatted <LI> tag - 
					Response.Write (string.Format("<li id='{0}'><span valign='bottom' title='{1}' onclick=\"javascript:if (Toggle(this))showContentsEx('divTree{0}','{0}','');\"><IMG  align='bottom' SRC='plus.gif'> <span class='treeStyleNode' >{1}</span></span><span id ='divTree{0}'></span></li>", 
						dv[i]["NodeID"].ToString(), dv[i]["NodeName"].ToString())); 
				}
				Response.Write ("</ul>"); 
			}
		}

		#region Web Form Designer generated code
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: This call is required by the ASP.NET Web Form Designer.
			//
			InitializeComponent();
			base.OnInit(e);
		}
		
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{    
			this.Load += new System.EventHandler(this.Page_Load);
		}
		#endregion

		 
	}
}