winform 網絡部分編程 ，瀏覽器，域名解析，下載網址內容

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Collections.Specialized;

namespace myone
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Application.Exit();
        }
        //域名解析
        private void button1_Click(object sender, EventArgs e)
        {
            if(txtUrl.Text!=string.Empty)
            {
                IPHostEntry host = Dns.GetHostEntry(txtUrl.Text);//獲取url的主機名
                foreach (IPAddress add in host.AddressList)//主機名的ip地址列表地址
                {
                    long ip = add.Address;//主機名的ip
                    listBox1.Items.Add(add.ToString());//加地址  255.255.255.255格式
                    listBox1.Items.Add(ip.ToString());//加ip  long 格式

                }
                textName.Text = host.HostName;//主機名（域名代理的狀況）
                textBroad.Text = IPAddress.Broadcast.ToString();//廣播地址

            }
            else
            {
                MessageBox.Show("請輸入網址！", "錯誤提示");
            }


        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }
        //下載數據
        private void button3_Click(object sender, EventArgs e)
        {
            WebClient clent = new WebClient();//
            Stream s = clent.OpenRead(textBox1.Text);//url  必須是http://www.baidu.com    http://www.google.com.hk 
            StreamReader reader = new StreamReader(s);//讀
            richTextBox1.Text = reader.ReadToEnd();//顯示
            reader.Close();
            s.Close();

        }
        //Header
        private void button4_Click(object sender, EventArgs e)
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(textBox1.Text);
            HttpWebResponse res = (HttpWebResponse)req.GetResponse();
            NameValueCollection headers = res.Headers;
            foreach(string name in headers)
            {
                listBox1.Items.Add(name + "-----" + headers[name]);
            }


        }
        //鏈接到  Navigate航行,跳轉
        private void button5_Click(object sender, EventArgs e)
        {
            textBox1.Text = "http://www.google.com.hk";
            webBrowser1.Navigate(textBox1.Text, false);
        }
    }
}