ListView中加复选框并实现全选（全不选）

using System;using System.Windows.Forms;using System.IO;namespace 带复选框的ListView{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();            this.Load += new EventHandler(Form1_Load);            this.button1.Click += new EventHandler(Button_Click);            this.button2.Click += new EventHandler(Button_Click);        }        private void Form1_Load(object sender, EventArgs e)        {            listView1.CheckBoxes = true;            listView1.View = View.Details;            listView1.GridLines = true;            listView1.Columns.Add("文件名称", 150, HorizontalAlignment.Left);            listView1.Columns.Add("创建时间", 200, HorizontalAlignment.Left);            DirectoryInfo di=new DirectoryInfo(@"D:\");            foreach (FileInfo fi in di.GetFiles())            {                ListViewItem lv = new ListViewItem();                lv.Text = fi.Name;                lv.SubItems.Add(fi.CreationTime.ToString());                listView1.Items.Add(lv);            }        }        private void Button_Click(object sender, EventArgs e)        {            Button b = (Button)sender;            if (b.Text == "全选")            {                foreach (ListViewItem item in listView1.Items)                {                    item.Checked = true;                }            }            else if (b.Text == "清空")            {                foreach (ListViewItem item in listView1.Items)                {                    item.Checked = false;                }            }        }    }}