提取网页中的链接并生成xml

using System;
using System.Xml;
using System.Text;
using System.Net;
using System.IO;
using System.Collections;
using System.Text.RegularExpressions;

public class App
{
    public static void Main()
    {
        string strCode;
        ArrayList alLinks;
        Console.Write("请输入一个网页地址：");
        string strURL = Console.ReadLine();
        if (strURL.Substring(0, 7) != @"http://")
        {
            strURL = @"http://" + strURL;
        }
        Console.WriteLine("正在获取页面代码，请稍侯...");
        strCode = GetPageSource(strURL);

        Console.WriteLine("正在提取超链接，请稍侯...");
        alLinks = GetHyperLinks(strCode);

        Console.WriteLine("正在写入文件，请稍侯...");
        WriteToXml(strURL, alLinks);
    }

    // 获取指定网页的HTML代码
    static string GetPageSource(string URL)
    {
        Uri uri = new Uri(URL);
        HttpWebRequest hwReq = (HttpWebRequest)WebRequest.Create(uri);
        HttpWebResponse hwRes = (HttpWebResponse)hwReq.GetResponse();
        hwReq.Method = "Get";
        hwReq.KeepAlive = false;
        StreamReader reader = new StreamReader(hwRes.GetResponseStream(), System.Text.Encoding.GetEncoding("GB2312"));
        return reader.ReadToEnd();
    }

    // 提取HTML代码中的网址
    static ArrayList GetHyperLinks(string htmlCode)
    {
        ArrayList al = new ArrayList();
        string strRegex = @"http://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
        Regex r = new Regex(strRegex, RegexOptions.IgnoreCase);
        MatchCollection m = r.Matches(htmlCode);
        for (int i = 0; i <= m.Count - 1; i++)
        {
            bool rep = false;
            string strNew = m[i].ToString();

            // 过滤重复的URL
            foreach (string str in al)
            {
                if (strNew == str)
                {
                    rep = true;
                    break;
                }
            }
            if (!rep) al.Add(strNew);
        }
        al.Sort();
        return al;
    }

    // 把网址写入xml文件
    static void WriteToXml(string strURL, ArrayList alHyperLinks)
    {
        XmlTextWriter writer = new XmlTextWriter("HyperLinks.xml", Encoding.UTF8);
        writer.Formatting = Formatting.Indented;
        writer.WriteStartDocument(false);
        writer.WriteDocType("HyperLinks", null, "urls.dtd", null);
        writer.WriteComment("提取自" + strURL + "的超链接");
        writer.WriteStartElement("HyperLinks");
        writer.WriteStartElement("HyperLinks", null);
        writer.WriteAttributeString("DateTime", DateTime.Now.ToString());
        foreach (string str in alHyperLinks)
        {
            string title = GetDomain(str);
            string body = str;
            writer.WriteElementString(title, null, body);
        }
        writer.WriteEndElement();
        writer.WriteEndElement();
        writer.Flush();
        writer.Close();
    }

    // 获取网址的域名后缀
    static string GetDomain(string strURL)
    {
        string retVal;
        string strRegex = @"(\.com/|\.net/|\.cn/|\.org/|\.gov/)";
        Regex r = new Regex(strRegex, RegexOptions.IgnoreCase);
        Match m = r.Match(strURL);
        retVal = m.ToString();
        strRegex = @"\.|/{1}quot;;
        retVal = Regex.Replace(retVal, strRegex, "").ToString();
        if (retVal == "")
            retVal = "other";
        return retVal;
    }
}