c#爬虫三类

-----------------提取网页内容----------------
1】
<<WebClient类>>
	WebClient wc = new WebClient();
    wc.Encoding = Encoding.UTF8;
    string str = wc.DownloadString("http://tieba.baidu.com/p/2314539885");//下载页面中所有的字符串
    MatchCollection mc = Regex.Matches(str, "([0-9a-zA-Z_.-]+)@([0-9a-zA-Z_.]+([.][a-zA-Z]+){1,2})");
   foreach (Match  item in mc)
   {
       if (item.Success)
       {
           Console.WriteLine(item.Groups[1].Value+"==="+item.Groups[2].Value);
       }
   }

   Console.WriteLine(mc.Count);
   Console.ReadKey();
	
	
或者》》	
 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.163.com”); //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
2】
<<WebRequest类>>
   public void RequestSite(string url)
   {
       WebRequest req = WebRequest.Create(url);
       HttpWebResponse res;
       try
       {
           res = (HttpWebResponse)(req.GetResponse());
       }
       catch (WebException ex) { res = (HttpWebResponse)ex.Response; }

       Stream st = res.GetResponseStream();
       StreamReader rdr = new StreamReader(st);
       string s = rdr.ReadToEnd();
       todo.AddRange(GetLink(s));
   }
   
3】
<<WebBrowser类>>//using System.Windows.Forms;估计是用在客户端的；
WebBrowser web = new WebBrowser(); 
web.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); 
            } 
        }