实在解决不了，求大神关于TreeView焦点改变后出现的有关问题 C# 2005 winform

实在解决不了，求大神关于TreeView焦点改变后出现的问题 C# 2005 winform
代码 C# 2005 winform 程序

测试程序代码如下：

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;


namespace WindowsApplication1 {

    public partial class Form1 : Form {

        public Form1() {

            InitializeComponent();

        }



        private void Form1_Load(object sender, EventArgs e) {


            this.treeView1.ImageList = imageList1;

            this.treeView1.Nodes.Clear();


            for (int i = 0; i < 5; i++) {

                TreeNode node = new TreeNode();

                node.Text = "根" + i.ToString();

                node.ImageIndex = 0;


                TreeNode node1 = new TreeNode();

                node1.Text = "1子" + i.ToString();

                node1.ImageIndex = 0;

                node.Nodes.Add(node1);


                TreeNode node2 = new TreeNode();

                node2.Text = "2子" + i.ToString();

                node2.ImageIndex = 0;

                node.Nodes.Add(node2);




                this.treeView1.Nodes.Add(node);

            }

        }



        private void button1_Click(object sender, EventArgs e) {


                this.treeView1.Nodes[0].Nodes[0].ImageIndex = 1;

                this.treeView1.Nodes[0].Nodes[1].ImageIndex = 1;

                this.treeView1.Nodes[0].ImageIndex = 1;

            

                this.treeView1.Nodes[1].Nodes[0].ImageIndex = 1;

                this.treeView1.Nodes[1].Nodes[1].ImageIndex = 0;

                this.treeView1.Nodes[1].ImageIndex = 2;

            

                this.treeView1.Nodes[2].Nodes[0].ImageIndex = 0;

                this.treeView1.Nodes[2].Nodes[1].ImageIndex = 1;

                this.treeView1.Nodes[2].ImageIndex = 2;

            

        }


        private void button2_Click(object sender, EventArgs e) {

            this.treeView1.Nodes[1].ImageIndex = 1;

        }


        private void button3_Click(object sender, EventArgs e) {

            this.treeView1.Nodes[0].ImageIndex = 1;

        }

    }

}

界面代码如下：

namespace WindowsApplication1 {

    partial class Form1 {