private void button1_Click(object sender, EventArgs e)

        {

            dataBind("", treeView1.Nodes);

        }

        public void dataBind(string code, TreeNodeCollection tnc)

        {

            foreach (ChinaStates cs in list)

            {

                if (cs.ParentAreaCode == code)

                {

                    TreeNode tn = new TreeNode(cs.AreaName);

                    tn.Tag = cs.AreaCode;

                    dataBind(cs.AreaCode, tn.Nodes);

                    tnc.Add(tn);

                }

            }

        }

        string tname = "";

        private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)

        {

            tname = "";

            getData(treeView1.SelectedNode);

            MessageBox.Show(tname.Substring(, tname.Length - ));

        }

        public void getData(TreeNode tn)

        {

            if (tn.Parent != null)

            {

                getData(tn.Parent);

            }

            tname += tn.Text + " | ";

        }

using System.Net;

using System.Net.Mail;

        //创建一个空的字符串

        string a = "";

        private void skinButton1_Click(object sender, EventArgs e)

        {

            //创建服务器对象

            SmtpClient smt = new SmtpClient("这里是域名");

            //创建发件人对象

            MailAddress my = new MailAddress("这里是发件人的邮箱");

            //创建收件人对象

            MailAddress you = new MailAddress("这里是收件人的邮箱");

            //创建邮件的对象,构造函数中传入发件人和收件人

            MailMessage mail = new MailMessage(my, you);//最后扔进这里面去

            //设置邮箱标题

            mail.Subject = "这是标题";

            //创建随机验证码

            string a1 = "abcdefghigklmnopqrstuvwxyzABCDEFGHIKIMNOPQRSTUVWXYZ0123456789";

            Random b = new Random();

            for (int i = ; i <= ; i++)

            {

                a += a1.Substring(b.Next(, a1.Length), );

            }

            //设置邮箱内容

            mail.Body = "验证码为:" + a;

            //创建互联网安全证书

            NetworkCredential nwcd = new NetworkCredential("发件人邮箱", "发件人邮箱的密码");

            //将证书绑定到服务器对象上,服务器验证

            smt.Credentials = nwcd;

            //发送验证码

            smt.Send(mail);

            //判断是否能走到这个地方,走到了就表示发送成功

            MessageBox.Show("发送成功!");

        }

        private void skinButton2_Click(object sender, EventArgs e)

        {

            //利用第二个TextBox判断是否输入的验证码正确

            if (skinTextBox2.Text == a)

            {

                MessageBox.Show("验证成功");

            }

            else

            {

                MessageBox.Show("失败");

            }

        }

 private void timer1_Tick(object sender, EventArgs e)

        {

            time--;

            button2.Text = "发送(" + time.ToString() + ")";

            if (time <= )

            {

                button2.Text = "发送";

                button2.Enabled = true;

                timer1.Enabled = false;

            }

        }