c#抓取网页数据

写了一个简单的抓取网页数据的小例子，代码如下：

  //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 = ;
             //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
         { 

         }
     return strResult;
     }
 //为了使用HttpWebRequest和HttpWebResponse，需填名字空间引用 

 //以下是程序具体实现过程：
     protected void btn_Click(object sender, EventArgs e)
     {
         //要抓取的URL地址
         string Url = "http://www.awtrip.com/";
         //得到指定Url的源码
         string strWebContent = GetWebContent(Url);
         //Response.Write(strWebContent);
         //取出和数据有关的那段源码
         int iBodyStart = strWebContent.IndexOf("<body", );
         int iStart = strWebContent.IndexOf("热门目的地旅游", iBodyStart);
         int iTableStart = strWebContent.IndexOf("<ul", iStart);
         int iTableEnd = strWebContent.IndexOf("</ul>", iTableStart);
         string strWeb = strWebContent.Substring(iTableStart, iTableEnd - iTableStart + );
         //生成HtmlDocument
         WebBrowser webb = new WebBrowser();
         webb.Navigate("about:blank");
         HtmlDocument htmldoc = webb.Document.OpenNew(true);
         htmldoc.Write(strWeb);
         HtmlElementCollection htmlTR = htmldoc.GetElementsByTagName("li");
         StringBuilder strlist = new StringBuilder();
         foreach (HtmlElement tr in htmlTR)
         {
             strlist.AppendFormat(tr.GetElementsByTagName("a")[].InnerText+"$");
         }
         Response.Write(strlist.ToString().Remove(strlist.ToString().Length-));
         ////最后再插入数据库 

     } 

引用：

using System.Net;
using System.IO;
using System.Text;
using System.Windows.Forms;

运行时可能为遇到“当前线程不在单线程单元中，因此无法实例化 ActiveX 控件”的问题，把aspx页面顶部的AutoEventWireup设置为ture就可以了