C# 最原始的tree 递归使用

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace EasyUITree
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        List<tree> listTreeAll = new List<tree>();

        tree treeAll = new tree();

        public tree BindNew(tree node)
        {
            DataTable dr = GetReader(node.id);
            tree n = new tree();
            for (int i = ; i < dr.Rows.Count; i++)
            {
                if (Convert.ToInt32(dr.Rows[i]["pid"]) == )
                {

                    n.id = Convert.ToInt32(dr.Rows[i]["id"]);
                    n.text = dr.Rows[i]["text"].ToString();
                    n.pid = Convert.ToInt32(dr.Rows[i]["pid"]);
                    n.child = GetChild(n);

                }
            }
            return n;
        }
        public List<tree> GetChild(tree node)
        {
            DataTable dr = GetReader(node.id);
            List<tree> child = new List<tree>();
            for (int i = ; i < dr.Rows.Count; i++)
            {

                tree n = new tree();
                n.id = Convert.ToInt32(dr.Rows[i]["id"]);
                n.text = dr.Rows[i]["text"].ToString();
                n.pid = Convert.ToInt32(dr.Rows[i]["pid"]);
                child.Add(n);
                DataTable dr1 = GetReader(n.id);
                if (dr1 != null)
                {
                    n.child = GetChild(n);
                }

            }
            return child;
        }

        

        /// <summary>
        /// 测试
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Button1_Click(object sender, EventArgs e)
        {
            tree model = new tree();
            model.id = ;
            BindNew(model);//递归

            List<tree> list = new List<tree>();
            list.Add(BindNew(model));

        }

        public DataTable GetReader(int pid)
        {
            string sql = " select * from t_tree where pid = " + pid + "  ";  //where pid = " + pid + "  ";
            string ConnectionString = "uid=sa;pwd=qazwsx;initial catalog=TestDBase;data source=DESKTOP-HKIRA54;Connect Timeout=900";
            using (SqlConnection con = new SqlConnection(ConnectionString))
            {
                SqlCommand cmd = new SqlCommand(sql, con);
                con.Open();
                DataSet ds = new DataSet();
                SqlDataAdapter adapter = new SqlDataAdapter();
                adapter.SelectCommand = cmd;
                adapter.Fill(ds);

                DataTable table = ds.Tables[];
                return table;
            }
        }
    }

    public class tree
    {
        public int id { get; set; }
        public string text { get; set; }
        public int pid { get; set; }
        public List<tree> child { get; set; }

    }