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;

using System.Data.SqlClient;

namespace 省市数据递归加载到TreeView

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            ////1.把所有的省份及直辖市加载到TreeView的根节点上。

            //List<Area> listProvince = GetSubItemByParentId(0);

            //foreach (Area item in listProvince)

            //{

            //    treeView1.Nodes.Add(item.AreaName);

            //}

            //递归将省市加载到TreeView中

            LoadDataToTree(treeView1.Nodes, );

        }

        //递归加载到TreeView

        private void LoadDataToTree(TreeNodeCollection treeNodeCollection, int pid)

        {

            //1.根据指定的pid获取该城市下的子城市

            List<Area> listCity = GetSubItemByParentId(pid);

            //2.遍历将获取到的数据绑定到treeNodeCollection节点集合中

            foreach (var item in listCity)

            {

                //返回刚刚增加的这个节点

                TreeNode node = treeNodeCollection.Add(item.AreaName);

                LoadDataToTree(node.Nodes, item.Areaid);

            }

        }

        //先封装一个方法，根据父Id查询下面的所有子项

        private List<Area> GetSubItemByParentId(int pid)

        {

            List<Area> list = new List<Area>();

            string sql = "select * from TblArea where areaPid=@pid";

            using (SqlDataReader reader = SqlHelper.ExecuteReader(sql, new SqlParameter("@pid", pid)))

            {

                if (reader.HasRows)

                {

                    while (reader.Read())

                    {

                        Area model = new Area();

                        model.Areaid = reader.GetInt32();

                        model.AreaName = reader.GetString();

                        model.AreaPid = reader.GetInt32();

                        list.Add(model);

                        /////不要直接在这里递归，一定要先把数据获取到一个集合中，然后再递归

                        /////否则会打开很多个连接。

                    }

                }

            }

            return list;

        }

    }

    public class Area

    {

        public int Areaid { get; set; }

        public string AreaName { get; set; }

        public int AreaPid { get; set; }

    }

}