动态提取网页中的图片地址

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




       StringBuilder html = new StringBuilder();//接收网页html字符串
        WebRequest request = WebRequest.Create("http://www.51rk.net/");
        request.Credentials = CredentialCache.DefaultCredentials;
        WebResponse response = request.GetResponse();
        Stream dataStream = response.GetResponseStream();
        StreamReader reader = new StreamReader(dataStream);
        string strTemp;
        while ((strTemp = reader.ReadLine()) != null)
        {
            html.Append(strTemp);
        }
        reader.Close();
        response.Close();       
        MatchCollection mc = Regex.Matches(html.ToString(), "<img.+?src=\"(?<url>.+?)\".+?>", RegexOptions.IgnoreCase);//验证图片
        foreach (Match m in mc)
        {
            Response.Write(m.Groups["url"].Value);//输出img地址