DHTML Tree View of Arbitrary Depth using AJAX

// Copyright (c)2005 Rewritten Software.  http://www.rewrittensoftware.com
// This script is supplied "as is" without any form of warranty. Rewritten Software 
// shall not be liable for any loss or damage to person or property as a result of using this script.
// Use this script at your own risk!
// You are licensed to use this script free of charge for commercial or non-commercial use providing you do not remove 
// the copyright notice or disclaimer.

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

/// <summary>
/// Summary description for Tree
/// </summary>
public class Tree
{
    private string id;

    /// <summary>
    /// The id to store the tree against in the session
    /// </summary>
    public string ID
    {
        get { return id; }
    }
	
    /// <summary>
    /// Constructor of the tree
    /// </summary>
    /// <param name="id"></param>
	public Tree(string id)
	{
        this.id = id;
        root = null;
	}

    private TreeNode root;

    /// <summary>
    /// The root node of the tree
    /// </summary>
    public TreeNode Root
    {
        get { return root; }
        set { root = value; }
    }
	
}

/// <summary>
/// A node in the tree
/// </summary>
public class TreeNode
{
    private string guid;

    /// <summary>
    /// Unique identifier for this node
    /// </summary>
    public string ID
    {
        get { return guid; }
    }

    private string text;

    /// <summary>
    /// The text to present on the tree node
    /// </summary>
    public string Text
    {
        get { return text; }
        set { text = value; }
    }

    private string url;

    /// <summary>
    /// URL to link to from tree node
    /// </summary>
    public string Url
    {
        get { return url; }
        set { url = value; }
    }

    private string imageClosed;

    /// <summary>
    /// Index of the image to show for the node
    /// </summary>
    public string ImageClosed
    {
        get { return imageClosed; }
        set { imageClosed = value; }
    }

    private string imageOpen;

    /// <summary>
    /// Image index to show when node is open
    /// </summary>
    public string ImageOpen
    {
        get { return imageOpen; }
        set { imageOpen = value; }
    }

    private System.Collections.ArrayList children = new System.Collections.ArrayList();

    /// <summary>
    /// A list of children of this node.
    /// </summary>
    public System.Collections.ArrayList Children
    {
        get { return children; }
        set { children = value; }
    }

    private bool expanded;

    /// <summary>
    /// Show the node as expanded or not.
    /// This does not reflect the runtime state of the tree, only the initial render
    /// state.
    /// </summary>
    public bool Expanded
    {
        get { return expanded; }
        set { expanded = value; }
    }


    /// <summary>
    /// Constructor for a treenode
    /// </summary>
    /// <param name="text">text to show</param>
    /// <param name="url">url to link to</param>
    /// <param name="imageIndexClosed">image to use</param>
    public TreeNode(string text, string url, string imageOpen, string imageClosed)
    {
        this.text = text;
        this.url = url;
        this.imageClosed = imageClosed;
        this.imageOpen = imageOpen;

        // Allocate a unique id for this node so it can be found again.
        this.guid = Guid.NewGuid().ToString();

        // Default is node will be collapsed.
        this.expanded = false;
    }

    /// <summary>
    /// Output the HTML to render a node and optionally fill in its children.
    /// </summary>
    /// <param name="writer"></param>
    /// <param name="treeID"></param>
    /// <param name="delayLoad"></param>
    public void WriteNode(HtmlTextWriter writer, string treeID, bool delayLoad)
    {

        // Work out which of plus, minus or empty to show.
        String plusImg = "plus.gif";
        if (this.Children.Count == 0)
            plusImg = "transparent.gif";
        else if (this.expanded)
            plusImg = "minus.gif";

        // Show the child if it is expanded
        String displayChild = "block";
        if (!this.Expanded)
            displayChild = "none";

        // Set up for the delay load call if the node is not loaded at this time
        string expand = String.Format("javascript:Toggle('{0}');", this.ID);
        if (!this.expanded && delayLoad)
            expand = String.Format("javascript:DelayLoadNode('{0}', '{1}');", treeID, this.ID);

        writer.Write("<table border=\"0\" cellpadding=\"1\" cellspacing=\"1\"><tr>");
        writer.Write(String.Format("<td width=\"16\"><a id=\"P{0}\" href=\"{1}\">", this.ID, expand));
        writer.Write(String.Format("<img src='img/{0}' width='16' height='16' hspace='0' vspace='0' border='0'/>", plusImg));
        writer.Write("</a></td>");
        writer.Write(String.Format("<td width=\"16\"><a id=\"I{0}\" href=\"{1}\">", this.ID, expand));
        writer.Write(String.Format("<img id='O{1}' style='display:{2}' src='{0}' width='16' height='16' hspace='0' vspace='0' border='0'/>", ImageOpen, this.ID, this.Expanded ? "block" : "none"));
        writer.Write(String.Format("<img id='C{1}' style='display:{2}' src='{0}' width='16' height='16' hspace='0' vspace='0' border='0'/>", ImageClosed, this.ID, this.Expanded ? "none" : "block"));
        writer.Write("</a></td>");
        writer.Write(String.Format("<td nowrap=\"true\"><a id=\"{0}\" href=\"{1}\">{2}</a></td>", this.ID, this.Url != null ? this.Url : "_blank", this.Text));
        writer.Write("</table>");

        // Content holder for the child nodes
        writer.Write(String.Format("<div style=\"display:{1};margin-left:2em\" id=\"D{0}\">", this.ID, displayChild));

        // And do the children only if we are not delay loading.
        if (!delayLoad)
        {
            foreach (TreeNode child in this.Children)
            {
                child.WriteNode(writer, treeID, delayLoad);
            }
        }

        writer.Write(String.Format("</div>"));
    }

}