httpwebrequest获取验证码图片

/// <summary>       /// 获取网页验证码       /// </summary>       /// <param name="server">服务器地址</param>       /// <param name="URL">网页地址</param>       /// <param name="byteRequest">字节数组，存放图片字节</param>       /// <param name="cookie">网站分配给客户的临时sessionid（临时cookie值），并非真正cookie</param>       /// <param name="header"></param>       /// <returns>图片的二进制数组</returns>        public static byte[] GetHtmlByBytes(string server, string URL, byte[] byteRequest, string cookie, out string header)        {            long contentLength; HttpWebRequest httpWebRequest;            HttpWebResponse webResponse;            Stream getStream;            httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(URL);            CookieContainer co = new CookieContainer();            co.SetCookies(new Uri(server), cookie);              httpWebRequest.CookieContainer = co;            httpWebRequest.ContentType = "application/x-www-form-urlencoded";            httpWebRequest.Method = "Post";            httpWebRequest.ContentLength = byteRequest.Length;            Stream stream;            stream = httpWebRequest.GetRequestStream();            stream.Write(byteRequest, 0, byteRequest.Length);            stream.Close();            webResponse = (HttpWebResponse)httpWebRequest.GetResponse();            header = webResponse.Headers.ToString();            getStream = webResponse.GetResponseStream();            contentLength = webResponse.ContentLength;            byte[] outBytes = new byte[contentLength];            outBytes = ReadFully(getStream);            getStream.Close();            return outBytes;        }