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 = 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 
        { 
            
        } 
    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", 0);
        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 + 5);
        //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")[0].InnerText+"$");
        }
        Response.Write(strlist.ToString().Remove(strlist.ToString().Length-1));
        ////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