public class MenuType
{
    public Guid Id { get; set; }
    public Guid PId { get; set; }
    public string MenuName { get; set; }
    public string Url { get; set; }
    public int OrderNum { get; set; }
    public int SonCount { get; set; }
}

protected void Page_Load(object sender, EventArgs e)
{
  if (Request["Action"] == "AJAX")
  {
    var result = GetMenu(Request["pid"]);
    JavaScriptSerializer serializer = new JavaScriptSerializer();
    string sRet = serializer.Serialize(result);
    Response.Write(sRet);
    Response.End();
  }
}

private List<MenuType> GetMenu(string pid)
{
  var result = new List<MenuType>();
  SqlConnection conn = new SqlConnection("Data Source=.;Initial Catalog=SHU;User ID=sa;Password=allen;");
  conn.Open();
  SqlCommand cmd = new SqlCommand();
  cmd.Connection = conn;
  cmd.CommandText = "select a.*,b.cout as count from Menu a left join (select COUNT(*) as cout,Menu.PId from Menu group by Menu.PId) as b on a.Id = b.PId where a.PId = '" + pid + "' order by OrderNum";
  SqlDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
  while (dr.Read())
  {
    var obj = new MenuType();
    obj.Id =Guid.Parse(dr["Id"].ToString());
    obj.MenuName = dr["MenuName"].ToString();
    obj.OrderNum = Convert.ToInt32(dr["OrderNum"]);
    obj.PId = dr["PId"] == DBNull.Value ? Guid.Empty : Guid.Parse(dr["PId"].ToString());
    obj.Url = dr["Url"].ToString();
    obj.SonCount = dr["count"] == DBNull.Value ? 0 : Convert.ToInt32(dr["count"]);
    result.Add(obj);
  }
  return result;
}

<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
  <link href="Scripts/themes/default/style.css" rel="stylesheet" type="text/css" />
  <script src="Scripts/jquery.js" type="text/javascript"></script>
  <script src="Scripts/jquery.jstree.js" type="text/javascript"></script>
  <script>
    $(function () {
      $.getJSON("/default.aspx?ACTION=AJAX&pid=00000000-0000-0000-0000-000000000000", function (result) {
        $.each(result, function (i, item) {
          var typeN = item.SonCount > 0 ? "jstree-closed" : "jstree-leaf";
          $("#tree").append("<li id='phtml_" + item.Id + "' class='" + typeN + "'><a href='#'>" + item.MenuName + "</a></li>");
        });
        $("#demo2").jstree({
          "plugins": ["themes", "html_data", 'types', "ui", "checkbox"],
          'core': { 'animation': 0 },
          "types": { "types":
                {
                  "person": { "icon": { "image": "/Scripts/themes/default/person.png"} },
                  "depar2": { "icon": { "image": "/Scripts/themes/default/depar2.png"} },
                  "default": { "icon": { "image": "/Scripts/themes/default/depar1.png"} }
                }
          }
        }).bind("open_node.jstree", function (e, data) {
          var id = data.rslt.obj[0].id;
          if ($("#" + id + " li").length > 0) { return; }
          $.getJSON("/default.aspx?ACTION=AJAX&pid=" + id.replace("phtml_", ""), function (result) {
            var str = "<ul>"
            $.each(result, function (i, item) {
              var typeN = item.SonCount > 0 ? "jstree-closed" : "jstree-leaf";
              var icon = item.SonCount > 0 ? "depar2" : "person";
              str += "<li rel = '" + icon + "' id='phtml_" + item.Id + "' class='" + typeN + "'><a href='#'> " + item.MenuName + "</a></li>";
            });
            str += "</ul>";
            $("#" + id).append(str);
            var tree = jQuery.jstree._reference("#" + id);
            tree.refresh();
            $("ins[class='jstree-checkbox jstree-icon']").removeClass("jstree-icon");
            $(".jstree-checkbox").attr("style", "");
          });
        });
      });
    });
  </script>
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
  <div id="demo2">
  <ul id="tree">
  </ul>
  </div>
</asp:Content>