懒加载树[tree]、点击已经加载完成的树[tree]节点，再次加载该节点下一级的所有子节点

1.先来一个div，如下：[设置:id=treeboxbox_tree,如下]

<td valign="top">
<div id="treeboxbox_tree" style=" 100%; height: 100%; float: left
border: 1px solid red;">
</div>
<br>
</td>

2.在页面加载后添加如下js代码：[每行代码意思都有解释]

tree = new dhtmlXTreeObject("treeboxbox_tree", "90%", "100%", 0);//treeboxbox_tree为上面的div的id；
tree.setSkin('dhx_skyblue'); //设这皮肤
tree.setImagePath("Dhx/samples/common/images/"); //设这图片的路径；
tree.enableDragAndDrop(1); //1表明可以drag； 0不可以drag；
tree.enableTreeLines(false);
tree.setOnClickHandler(onOneClick);//绑定onOneClick()方法；当单击树的节点是触发click事件；
tree.setXMLAutoLoading("ResponseXml.ashx");
tree.loadXML("ResponseXml.ashx?id=0");//请求的一般处理程序，下面将给出源码；?id=0,说明当页面加载的时候请求的是0级的节点集合；

3.后台一般处理程序如下:

 /// <summary>
    /// ResponseXml 的摘要说明
    /// </summary>
    public class ResponseXml : IHttpHandler
    {
        private string id = HttpContext.Current.Request["id"] ?? "";
        private bool root = true;

        private Kyt.BLL.base_productclass2 baseProductclass2 = new base_productclass2();

        public void ProcessRequest(HttpContext context)
        {
            //       context.Response.ContentType = "text/plain";
            context.Response.ContentType = "text/html";
            XmlDocument document = new XmlDocument();
            XmlElement rootEle = document.CreateElement("tree");
            XmlDeclaration declaration = document.CreateXmlDeclaration("1.0", "utf-8", "");
            document.InsertBefore(declaration, document.DocumentElement);
            document.AppendChild(rootEle);
            if (id == "0")
            {
                rootEle.SetAttribute("id", "0");
            }
            else
            {
                rootEle.SetAttribute("id", id);
            }
            List<Kyt.Model.base_productclass2> list = listChildren(id);
            foreach (var itemList in list)
            {
                XmlElement element = document.CreateElement("item");
                element.SetAttribute("text", itemList.mc);
                rootEle.AppendChild(element);
                element.SetAttribute("id", itemList.cpbm);
                if (itemList.sy)
                {//child 为0表明是树叶，为1表明不是树叶
                    element.SetAttribute("child", "0");
                }
                else
                {
                    element.SetAttribute("child", "1");
                }
            }
            XmlWriter w = new XmlTextWriter(context.Response.OutputStream, Encoding.UTF8);
            document.WriteTo(w);
            w.Flush();
            w.Close();

            //  document.Save(context.Request.MapPath("test.xml"));
            //     context.Response.Write("<script>location='test.xml'</script>");

        }

        /// <summary>
        /// 列出写几编码，只列出直接的下级。如果参数为null，列出第一级别；
        /// </summary>
        /// <param name="cpbm"></param>
        /// <returns></returns>
        private List<Kyt.Model.base_productclass2> listChildren(string cpbm)
        {
            Kyt.BLL.base_productclass2 baseProductclass2 = new base_productclass2();
            if (cpbm != null)
            {
                Kyt.Model.base_productclass2 parent = baseProductclass2.GetModel(cpbm);
                int level = parent.jc.Value + 1;
                return baseProductclass2.GetModelList(" cpbm like '" + cpbm + "%' and jc=" + level.ToString());
            }
            else
            {
                return baseProductclass2.GetModelList("jc=0");
            }
        }

 4.aspx页面要引用的文件，代码如下：

<link href="Jquery_ui/themes/base/jquery.ui.all.css" rel="stylesheet" type="text/css" />
<script src="../scripts/jquery-1.4.1-vsdoc.js" type="text/javascript"></script>
<script src="Jquery_ui/themes/jquery-ui.js" type="text/javascript"></script>
<link href="Dhx/codebase/dhtmlxtree.css" rel="stylesheet" type="text/css" />
<script src="Dhx/codebase/dhtmlxcommon.js" type="text/javascript"></script>
<script src="Dhx/codebase/dhtmlxtree.js" type="text/javascript"></script>
dhx资源地址：http://dhtmlx.com/docs/products/dhtmlxTree/的找download，

至于juqery ui ，就很好找了，在这里就不多说了！

对于jquery ui 和dhx，找找demo，看看例子，有时候做项目有很大的用处！

5.要实现的树的结果图,如下：

当添加、删除、更新一个节点之后，要对该节点刷新-tree.refreshItem(id);//id为要刷新的节点id