抓取网站正则表达式

    //获取论坛最新贴
        public string GetBBSTopic(int pageSize) 
        {
            StringBuilder builder = new StringBuilder();
            string url = "http://www.globevisa.com.cn/vbb/forumdisplay.php?f=7";//投资移民
            string content = WebUtils.PostResponse(url, "");

            string pattern = "<a(.*?)href=\"(.*?)\">(.*?)</a>";
            //  pattern = "\n<li><span class=\"middate\">2009-05-22 11:30</span>\n[<a target=\"_blank\" href=\"http://stock.eastmoney.com/company/1175.html\">金证顾问</a>] <a target=\"_blank\" href=\"http://news2.eastmoney.com/090522,1049,1087911.html\">午评：银行企稳 助大盘反弹</a></li>";
            //时间 类别URL 类别 资讯URL 资讯

            Regex r = new Regex(pattern, RegexOptions.Singleline);
            MatchCollection mc = r.Matches(content);

            int num = 0;
            foreach (Match m in mc)
            { 
                string aUrl  = m.Result("$2");
                string title = m.Result("$3");
                if (aUrl.IndexOf("showthread.php") != -1 && title.Length > 4 && title.IndexOf("<img") == -1)
                {
                    //useful
                    if (num < pageSize)
                    {
                        builder.Append("<li class=\"bbsLi\">\r\n");
                        builder.AppendFormat("<a href=\"http://www.globevisa.com.cn/vbb/{0}\" target='_blank' title=\"{2}\">{1}</a>\r\n", aUrl,StringUtils.GetGoodString(WebUtils.FilterHtml(title),24),title);
                        builder.Append("</li>\r\n");
                    }
                    else
                    {
                        break;
                    }
                    num++;
                }
            }
            return builder.ToString();
          
        }