关于ASP.NET中TreeView用法的一个小例子

代码如下:
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Data.SqlClient;
using Common;
using DataAccess;

public partial class Controls_ProductType2 : System.Web.UI.UserControl
{

    ProductType productType = new ProductType();
    Product product = new Product();

  protected void TreeView_TreeNodePopulate(object sender, TreeNodeEventArgs e)
    {

        if (e.Node.ChildNodes.Count == 0)
        {
            switch (e.Node.Depth)
            {
                case 0:
                    PopulateCategories(e.Node);
                    break;
                case 1:
                    PopulateProductType(e.Node);
                    break;
                case 2:
                    PopulateProducts(e.Node);
                    break;
            }
        }

      //  int i = TreeToXml.TreeToXML(TreeView1, "D:/TreeToXML.xml");

    }

    protected void Page_Load(object sender, EventArgs e)
    {

    }

    //第一级节点（parentID=0）
    void PopulateCategories(TreeNode node)
    {
        DataTable dt = new DataTable();
        dt = productType.GetListByFatherNode();

        if (dt.Rows.Count > 0)
        {
            foreach (DataRow row in dt.Rows)
            {