winform 网络部分编程 ，浏览器，域名解析，下载网址内容

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);//获取url的主机名
                foreach (IPAddress add in host.AddressList)//主机名的ip地址列表地址
                {
                    long ip = add.Address;//主机名的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;//主机名（域名代理的情况）
                textBroad.Text = IPAddress.Broadcast.ToString();//广播地址

            }
            else
            {
                MessageBox.Show("请输入网址！", "错误提示");
            }


        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }
        //下载数据
        private void button3_Click(object sender, EventArgs e)
        {
            WebClient clent = new WebClient();//
            Stream s = clent.OpenRead(textBox1.Text);//url  必须是http://www.baidu.com    http://www.google.com.hk 
            StreamReader reader = new StreamReader(s);//读
            richTextBox1.Text = reader.ReadToEnd();//显示
            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]);
            }


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