Проблема с Пост запросом отправка AMF

        private void button1_Click(object sender, EventArgs e)
        {
            String s1 = "{\"error\":{\"error_code\":3,\"error_msg\":\"Unknown method passed\",\"request_params\":-[{\"key\":\"method\",\"value\":\"get\"},{\"key\":\"format\",\"value\":\"JSON\"},{\"key\":\"sid\",\"value\":\"f79c36dd75f5910d704246cb7ca5083cfc6016d58e4d070e848914fbefa780\"},{\"key\":\"v\",\"value\":\"3.0\"},{\"key\":\"api_id\",\"value\":\"35569\"},{\"key\":\"sig\",\"value\":\"2d6f4c68cf5e8201d84c9742ecb21665\"}]}}";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://109.234.157.37/prison/universal.php?getCityInfo");
            request.UserAgent = "Mozilla/5.0";
            request.Method = "POST";
            //request.Proxy = new WebProxy(ip, port);
            request.ContentType = "application/x-www-form-urlencoded";
            byte[] EncodedPostParams = Encoding.ASCII.GetBytes(s1);
            request.ContentLength = EncodedPostParams.Length;
            request.GetRequestStream().Write(EncodedPostParams, 0, EncodedPostParams.Length);
            request.GetRequestStream().Close();
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            string html = new StreamReader(response.GetResponseStream(), Encoding.UTF8).ReadToEnd();
        }