public static string GetHtml(string url)
        {
            string html = "";
            try
            {
                WebClient MyWebClient = new WebClient();

                Encoding utf8 = Encoding.UTF8;

                Encoding defaultCode = Encoding.Default;

                MyWebClient.Credentials = CredentialCache.DefaultCredentials;//获取或设置用于对向Internet资源的请求进行身份验证的网络凭据。

                Byte[] pageData = MyWebClient.DownloadData(url);//从指定网站下载数据
                string pageHtml = Encoding.Default.GetString(pageData);
                string Encodeing = getEncoding(pageHtml);
                if (Encodeing != "GB2312" && Encodeing != "GBK")
                {
                    byte[] defaultBytes = Encoding.Convert(utf8, defaultCode, pageData);
                    pageHtml = Encoding.Default.GetString(defaultBytes);  //如果获取网站页面采用的是GB2312，则使用这句  
                }

                html = pageHtml;
            }
            catch (WebException webEx)
            {
                Console.WriteLine(webEx.Message.ToString());
            }
            return html;
        }

        public static string getEncoding(string html)
        {
            Match match = Regex.Match(html, "charset=(?\'ecncoding\'.*[\\d|k|K])\"");
            GroupCollection groups = match.Groups;
            string ecncoding = groups["ecncoding"].Value;
            return ecncoding.ToUpper();
        }

        protected void btnOk_Click(object sender, EventArgs e)
        {
            lstEmails.Items.Clear();
            string html = GetHtml(this.txturl.Text.Trim());
            string reg = @"[a-zA-Z0-9_\-\.]+@\w+(\.\w+)+";//匹配Email的正则表达式
            MatchCollection matchs = Regex.Matches(html, reg);foreach (Match ms in matchs)
            {
                txtEmails.Items.Add(new ListItem(ms.Value+",\r\n"));
            }
        }