三种asp.net 抓取网页源代码，推荐方法一

        /// <summary>方法一：比较推荐
        /// 用HttpWebRequest取得网页源码
        /// 对于带BOM的网页很有效，不管是什么编码都能正确识别
        /// </summary>
        /// <param name="url">网页地址" </param>
        /// <returns>返回网页源文件</returns>
        public static string GetHtmlSource2(string url)
        {
            //处理内容
            string html = "";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Accept = "*/*"; //接受任意文件
            request.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.1.4322)"; // 模拟使用IE在浏览 http://www.52mvc.com
            request.AllowAutoRedirect = true;//是否允许302
            //request.CookieContainer = new CookieContainer();//cookie容器，
            request.Referer = url; //当前页面的引用
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream stream = response.GetResponseStream();
            StreamReader reader = new StreamReader(stream, Encoding.Default);
            html = reader.ReadToEnd();
            stream.Close();
            return html;
        }
        

        //方法二：
        public static string GetHttpData2(string Url)
        {
            string sException = null;
            string sRslt = null;
            WebResponse oWebRps = null;
            WebRequest oWebRqst = WebRequest.Create(Url);
            oWebRqst.Timeout = 50000;
            try
            {
                oWebRps = oWebRqst.GetResponse();
            }
            catch (WebException e)
            {
                sException = e.Message.ToString();
            }
            catch (Exception e)
            {
                sException = e.ToString();
            }
            finally
            {
                if (oWebRps != null)
                {
                    StreamReader oStreamRd = new StreamReader(oWebRps.GetResponseStream(), Encoding.GetEncoding("utf-8"));
                    sRslt = oStreamRd.ReadToEnd();
                    oStreamRd.Close();
                    oWebRps.Close();
                }
            }
            return sRslt;
        }


        /// <summary>方法三：
        ///
        /// </summary>
        /// <param name="url">/要访问的网站地址</param>
        /// <param name="charSets">目标网页的编码，如果传入的是null或者"",那就自动分析网页的编码</param>
        /// <returns></returns>
        public static string getHtml(string url, params  string[] charSets)
        {
            try
            {
                string charSet = null;
                if (charSets.Length == 1)
                {
                    charSet = charSets[0];
                }
                WebClient myWebClient = new WebClient(); //创建WebClient实例myWebClient
                // 需要注意的：
                //有的网页可能下不下来，有种种原因比如需要cookie,编码问题等等
                //这是就要具体问题具体分析比如在头部加入cookie
                // webclient.Headers.Add("Cookie", cookie);
                //这样可能需要一些重载方法.根据需要写就可以了
                //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.
                myWebClient.Credentials = CredentialCache.DefaultCredentials;
                //如果服务器要验证用户名，密码
                //NetworkCredential mycred = new NetworkCredential(struser, strpassword);
                //myWebClient.Credentials = mycred;
                //从资源下载数据并返回字节数组.(加@是因为网址中间有"/"符号)
                byte[] myDataBuffer = myWebClient.DownloadData(url);
                string strWebData = Encoding.Default.GetString(myDataBuffer);
                //获取网页字符编码描述信息
                Match charSetMatch = Regex.Match(strWebData, "<meta([^<]*)charset=([^<]*)", RegexOptions.IgnoreCase | RegexOptions.Multiline);
                string webCharSet = charSetMatch.Groups[2].Value;
                if (charSet == null || charSet == "")
                    charSet = webCharSet;
                if (charSet != null && charSet != "" && Encoding.GetEncoding(charSet) != Encoding.Default)
                {
                    strWebData = Encoding.GetEncoding(charSet).GetString(myDataBuffer);
                }
                else
                {
                    strWebData = Encoding.GetEncoding("utf-8").GetString(myDataBuffer);
                }
                return strWebData;
            }
            catch (Exception e) { return ""; }
        }