treeview递归加载

实体类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WindowsFormsApplication2
{
    public class China
    {
        public string AreaCode { get; set; }
        public string AreaName { get; set; }
        public string ParentAreaCode { get; set; }

    }
}

数据访问类：

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Text;

namespace WindowsFormsApplication2
{
    public class ChinaData
    {
        SqlConnection conn = null;
        SqlCommand cmd = null;

        public ChinaData()
        {
            conn = new SqlConnection("server=.;database=mydb;user=sa;pwd=123");
            cmd = conn.CreateCommand();
        }

        public List<China> Select(string pcode)
        {
            List<China> clist = new List<China>();

            cmd.CommandText = "select *from ChinaStates where ParentAreaCode = '" + pcode + "'";

            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    China c = new China();
                    c.AreaCode = dr[].ToString();
                    c.AreaName = dr[].ToString();
                    c.ParentAreaCode = dr[].ToString();

                    clist.Add(c);
                }
            }

            conn.Close();
            return clist;
        }

        public List<China> Select()
        {
            List<China> clist = new List<China>();

            cmd.CommandText = "select *from ChinaStates";

            conn.Open();
            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    China c = new China();
                    c.AreaCode = dr[].ToString();
                    c.AreaName = dr[].ToString();
                    c.ParentAreaCode = dr[].ToString();

                    clist.Add(c);
                }
            }

            conn.Close();
            return clist;
        }

    }
}

form1：treeview 使用递归

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        List<China> AllList = new List<China>();

        public Form1()
        {
            InitializeComponent();

            AllList = new ChinaData().Select();

            TreeNode tn1 = new TreeNode("中国");
            tn1.Tag = "";

            NodesBind(tn1);

            treeView1.Nodes.Add(tn1);

        }

        public void NodesBind(TreeNode tn)
        {
            //lambda 表达式
            List<China> clist = AllList.Where(r => r.ParentAreaCode == tn.Tag.ToString()).ToList();

            foreach (China c in clist)
            {
                TreeNode tnn = new TreeNode(c.AreaName);
                tnn.Tag = c.AreaCode;

                NodesBind(tnn);

                tn.Nodes.Add(tnn);
            }
        }

    }
}