网页抓取数据并分析，特别包括分页数据的抓取。

包括8个按钮，每个按钮下的代码都可运行（第5、6个可能需要调试一下）。

有基本的页面抓取，不含分页数据的；

有含分页数据，且【下一页】的链接是网址的；

有含分页数据，且【下一页】的链接是__doPostBack；

有含分页数据，且【下一页】的属性是.gif，可通过F12找到href的。

参考网址：http://www.cnblogs.com/ceachy/articles/CSharp_Retrive_Page_Document.html

http://www.cnblogs.com/ghfsusan/archive/2010/05/26/1744820.html

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.IO;
using  System.Net;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //private void button1_Click(object sender, EventArgs e)
        //{
        //    MessageBox.Show("hello world.");
        //}

        //WebBrowser web1 = new WebBrowser(); 
        //web1.Navigate("http://www.xjflcp.com/ssc/"); 
        //web.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(web_DocumentCompleted); 
        //void web_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) 
        //{ 
        //    WebBrowser web = (WebBrowser)sender; 
        //    HtmlElementCollection ElementCollection = web.Document.GetElementsByTagName("Table"); 
        //    foreach (HtmlElement item in ElementCollection) 
        //    { 
        //         File.AppendAllText("Kaijiang_xj.txt", item.InnerText); 
        //    } 
        //}

        
        //根据Url地址得到网页的html源码 
        private string GetWebContent(string Url) 
        { 
            string strResult=""; 
            try 
            { 
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url); //声明一个HttpWebRequest请求 
                request.Timeout = 30000; //设置连接超时时间 
                request.Headers.Set("Pragma", "no-cache"); 
                HttpWebResponse response = (HttpWebResponse)request.GetResponse(); 
                Stream streamReceive = response.GetResponseStream(); 
                Encoding encoding = Encoding.GetEncoding("GB2312"); 
                StreamReader streamReader = new StreamReader(streamReceive, encoding); 
                strResult = streamReader.ReadToEnd(); 
            } 
            catch 
            { 
                MessageBox.Show("出错"); 
            } 
            return strResult; 
        } 
        //为了使用HttpWebRequest和HttpWebResponse，需填名字空间引用 using System.Net; 
        //以下是程序具体实现过程： 
        private void button1_Click(object sender, EventArgs e) 
        {
            //要抓取的URL地址
            string Url = "http://list.mp3.baidu.com/topso/mp3topsong.html?id=1#top2";
            //得到指定Url的源码
            string strWebContent = GetWebContent(Url);
            richTextBox1.Text = strWebContent;
            //取出和数据有关的那段源码
            int iBodyStart = strWebContent.IndexOf("<body", 0);
            int iStart = strWebContent.IndexOf("歌曲TOP500", iBodyStart);
            int iTableStart = strWebContent.IndexOf("<table", iStart);
            int iTableEnd = strWebContent.IndexOf("</table>", iTableStart);
            string strWeb = strWebContent.Substring(iTableStart, iTableEnd - iTableStart + 8);
            //生成HtmlDocument
            WebBrowser webb = new WebBrowser();
            webb.Navigate("about:blank");
            HtmlDocument htmldoc = webb.Document.OpenNew(true);
            htmldoc.Write(strWeb);
            HtmlElementCollection htmlTR = htmldoc.GetElementsByTagName("TR");
            foreach (HtmlElement tr in htmlTR)
            {
                string strID = tr.GetElementsByTagName("TD")[0].InnerText;
                string strName = tr.GetElementsByTagName("TD")[1].InnerText;
                string strSinger = tr.GetElementsByTagName("TD")[1].InnerText;
                //插入DataTable
                strID = strID.Replace(".", "");
                //AddLine(strID, strName, strSinger, "0");

                //string strID = tr.GetElementsByTagName("TD")[0].InnerText;
                //string strName = SplitName(tr.GetElementsByTagName("TD")[1].InnerText, "MusicName");
                //string strSinger = SplitName(tr.GetElementsByTagName("TD")[1].InnerText, "Singer");
                ////插入DataTable
                //strID = strID.Replace(".", "");
                //AddLine(strID, strName, strSinger, "0");

                //string strID1 = tr.GetElementsByTagName("TD")[2].InnerText;
                //string strName1 = SplitName(tr.GetElementsByTagName("TD")[3].InnerText, "MusicName");
                //string strSinger1 = SplitName(tr.GetElementsByTagName("TD")[3].InnerText, "Singer");
                ////插入DataTable
                //strID1 = strID1.Replace(".", "");
                //AddLine(strID1, strName1, strSinger1, "0");

                //string strID2 = tr.GetElementsByTagName("TD")[4].InnerText;
                //string strName2 = SplitName(tr.GetElementsByTagName("TD")[5].InnerText, "MusicName");
                //string strSinger2 = SplitName(tr.GetElementsByTagName("TD")[5].InnerText, "Singer");
                ////插入DataTable
                //strID2 = strID2.Replace(".", "");
                //AddLine(strID2, strName2, strSinger2, "0");
            }
            //插入数据库
            //InsertData(dt);

            //dataGridView1.DataSource = dt.DefaultView;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            try {
                WebClient MyWebClient = new WebClient();
                MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
                Byte[] pageData = MyWebClient.DownloadData("http://bbs.cup.edu.cn/cupbbs/ThreadList.aspx?fid=51"); //从指定网站下载数据
                //string pageHtml = Encoding.Default.GetString(pageData);  //如果获取网站页面采用的是GB2312，则使用这句            
                string pageHtml = Encoding.UTF8.GetString(pageData); //如果获取网站页面采用的是UTF-8，则使用这句
                Console.WriteLine(pageHtml);//在控制台输入获取的内容
                using (StreamWriter sw = new StreamWriter("C:\\Users\\yuan\\Desktop\\ouput.html"))//将获取的内容写入文本
                {
                    sw.Write(pageHtml);
                }
                Console.ReadLine(); //让控制台暂停,否则一闪而过了             
            }
            catch(WebException webEx) {
                Console.WriteLine(webEx.Message.ToString());
            }
        }

        void web_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            WebBrowser web = (WebBrowser)sender;
            HtmlElementCollection ElementCollection = web.Document.GetElementsByTagName("Table");
            foreach (HtmlElement item in ElementCollection)
            {
                File.AppendAllText("C:\\Users\\yuan\\Desktop\\ouputbutton3.txt", item.InnerText);
            }
        }
        private void button3_Click(object sender, EventArgs e)
        {
            WebBrowser web = new WebBrowser();
            web.Navigate("http://www.chinahighway.gov.cn/html/staticHtml/front/index_lkcx.html"); 
            web.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(web_DocumentCompleted); 
        }

        private void button4_Click(object sender, EventArgs e)
        {
            string _StrResponse = "";
            HttpWebRequest _WebRequest = (HttpWebRequest)WebRequest.Create("http://bbs.cup.edu.cn/cupbbs/ThreadList.aspx?fid=51");
            _WebRequest.UserAgent = "MOZILLA/4.0 (COMPATIBLE; MSIE 7.0; WINDOWS NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)";
            _WebRequest.Method = "Get";
            WebResponse _WebResponse = _WebRequest.GetResponse();
            StreamReader _ResponseStream = new StreamReader(_WebResponse.GetResponseStream(), System.Text.Encoding.GetEncoding("gb2312"));
            _StrResponse = _ResponseStream.ReadToEnd();
            _WebResponse.Close();
            _ResponseStream.Close();
            File.AppendAllText("C:\\Users\\yuan\\Desktop\\ouputbutton4.txt", _StrResponse);
        }

        private void button5_Click(object sender, EventArgs e)
        {
            System.Net.WebClient WebClientObj = new System.Net.WebClient();
            System.Collections.Specialized.NameValueCollection PostVars = new System.Collections.Specialized.NameValueCollection();
            PostVars.Add("__VIEWSTATE", "dDwxNDMyMjQ3NTY4O3Q8O2w8aTwxPjs+O2w8dDw7bDxpPDM+O2k8Nz47PjtsPHQ8O2w8aTwwPjtpPDE+O2k8Mj47aTwzPjtpP........省略了，太长了.......");
            //PostVars.Add("__EVENTVALIDATION", "此处是您需要提前得到的信息");
            PostVars.Add("__EVENTTARGET", "grdThreadList:_ctl27:_ctl3");
            //PostVars.Add("__EVENTARGUMENT", "");
            //string s = "23$74$56";
            //string[] str=new string[5];
            //str=s.Split('$');
            WebClientObj.Headers.Add("ContentType", "application/x-www-form-urlencoded");
            try
            {
                byte[] byte1 = WebClientObj.UploadValues("http://bbs.cup.edu.cn/cupbbs/ThreadList.aspx?fid=51", "POST", PostVars);
                string ResponseStr = Encoding.UTF8.GetString(byte1); //得到当前页面对应的html 文本字符串
                //GetPostValue(ResponseStr);//得到当前页面对应的 __VIEWSTATE 等上面需要的信息，为抓取下一页面使用
                //SaveMessage(ResponseStr);//保存自己关心的内容到数据库中
                File.AppendAllText("C:\\Users\\yuan\\Desktop\\ouputbutton5.txt", ResponseStr);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }

        private static string current__viewstate="";//保存当前页面对应的 __VIEWSTATE 等上面需要的信息，为再次点击按钮（抓取下一页面）使用
        private string GetPostValue(string ResponseStr)
        {
            //......
            return "";//略//解析ResponseStr，得到__VIEWSTATE的值
        }
        private void button6_Click(object sender, EventArgs e)
        {
            System.Net.WebClient WebClientObj = new System.Net.WebClient();
            System.Collections.Specialized.NameValueCollection PostVars = new System.Collections.Specialized.NameValueCollection();
            PostVars.Add("__VIEWSTATE", current__viewstate);
            ////PostVars.Add("__EVENTVALIDATION", "此处是您需要提前得到的信息");
            PostVars.Add("__EVENTTARGET", "grdThreadList:_ctl27:_ctl3");//通过for,改变其值，ctl1,ctl2,ctl3....
            ////PostVars.Add("__EVENTARGUMENT", "");
            ////string s = "23$74$56";
            ////string[] str=new string[5];
            ////str=s.Split('$');
            WebClientObj.Headers.Add("ContentType", "application/x-www-form-urlencoded");
            try
            {
                byte[] byte1 = WebClientObj.UploadValues("http://www.chinahighway.gov.cn/html/staticHtml/front/index_lkcx.html", "POST", PostVars);
                string ResponseStr = Encoding.UTF8.GetString(byte1); //得到当前页面对应的html 文本字符串
                current__viewstate=GetPostValue(ResponseStr);//得到当前页面对应的 __VIEWSTATE 等上面需要的信息，为抓取下一页面使用
                //SaveMessage(ResponseStr);//保存自己关心的内容到数据库中
                File.AppendAllText("C:\\Users\\yuan\\Desktop\\ouputbutton6.txt", ResponseStr);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }

        private void button7_Click(object sender, EventArgs e)
        {
            try
            {
                WebClient MyWebClient = new WebClient();
                MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
                Byte[] pageData = MyWebClient.DownloadData("http://gb.cri.cn/42071/2013/03/05/3245s4038640_2.htm"); //从指定网站下载数据
                string pageHtml = Encoding.Default.GetString(pageData);  //如果获取网站页面采用的是GB2312，则使用这句            
                //string pageHtml = Encoding.UTF8.GetString(pageData); //如果获取网站页面采用的是UTF-8，则使用这句
                Console.WriteLine(pageHtml);//在控制台输入获取的内容
                using (StreamWriter sw = new StreamWriter("C:\\Users\\yuan\\Desktop\\ouput7.html"))//将获取的内容写入文本
                {
                    sw.Write(pageHtml);
                }
                Console.ReadLine(); //让控制台暂停,否则一闪而过了             
            }
            catch (WebException webEx)
            {
                Console.WriteLine(webEx.Message.ToString());
            }
        }

        //对分页数据抓取，当网页上【下一页】的属性是.gif格式的时候，而且鼠标停在【下一页】上面，页面下面显示的网址不完整（网址太长，只能看到部分），
        //可以通过在网页上点击右键【查看源文件】,或F12【脚本】，找到对应的href，即可得到网址。
        private void button8_Click(object sender, EventArgs e)
        {
            try
            {
                WebClient MyWebClient = new WebClient();
                MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于向Internet资源的请求进行身份验证的网络凭据
                Byte[] pageData = MyWebClient.DownloadData("http://www.chinahighway.gov.cn/roadInfo/queryRoadInfo.do?queryType=map&startDate=&cantonName=&cantonCode=&infoType=3&endDate=&startPlanDate=&_page_size=50&roadName=&mapList=-1&endRealDate=&roadCode=&provinceList=-1&endPlanDate=&startRealDate=&page=3"); //从指定网站下载数据
                string pageHtml = Encoding.Default.GetString(pageData);  //如果获取网站页面采用的是GB2312，则使用这句            
                //string pageHtml = Encoding.UTF8.GetString(pageData); //如果获取网站页面采用的是UTF-8，则使用这句
                Console.WriteLine(pageHtml);//在控制台输入获取的内容
                using (StreamWriter sw = new StreamWriter("C:\\Users\\yuan\\Desktop\\ouput8.txt"))//将获取的内容写入文本
                {
                    sw.Write(pageHtml);
                }
                Console.ReadLine(); //让控制台暂停,否则一闪而过了             
            }
            catch (WebException webEx)
            {
                Console.WriteLine(webEx.Message.ToString());
            }
        }


    }
}