using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;namespace treeview1
{public partial class Form1 : Form{public Form1(){InitializeComponent();}// 首先将所有数据读取出来，在进行递归排列List<Info> list = new List<Info>();private void Form1_Load(object sender, EventArgs e){InitData();AddTree(0, null);}void InitData(){SqlConnection conn = new SqlConnection("server=PC201609230944\\SQL2005;database=HeiMaBlog;user=sa;pwd=123456");SqlCommand cmd = new SqlCommand("select * from Area", conn);conn.Open();SqlDataReader dr = cmd.ExecuteReader();if (dr.HasRows){while (dr.Read()){Info nin = new Info() { Ar_id = dr.GetInt32(0), Ar_name = dr[1].ToString(), Ar_uid = dr.GetInt32(2) };list.Add(nin);}}}// 递归// 父id和父节点// 省：父id = 0，父节点是trMainvoid AddTree(int pid, TreeNode pnod){foreach (Info item in list){if (item.Ar_uid == pid){// 新建一个节点，并且给节点赋值TreeNode tnod = new TreeNode();tnod.Text = item.Ar_name;if (pnod == null){// 父节点为null，添加到trMain
                        trMain.Nodes.Add(tnod);}else{//不是，就添加到父级点上
                        pnod.Nodes.Add(tnod);}AddTree(item.Ar_id, tnod);}}}}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;namespace treeview1
{class Info{/// <summary>/// 地区编号/// </summary>int ar_id;public int Ar_id{get { return ar_id; }set { ar_id = value; }}/// <summary>/// 地区名字/// </summary>string ar_name;public string Ar_name{get { return ar_name; }set { ar_name = value; }}/// <summary>/// 地区父级/// </summary>int ar_uid;public int Ar_uid{get { return ar_uid; }set { ar_uid = value; }}}
}