public class usuario
        {
            public string success { get; set; }
            public string errorMessage { get; set; }
            public string answer { get; set; }
            public string token { get; set; }

           public usuario()
            {
                this.success = success;
                this.errorMessage = errorMessage;
                this.answer = answer;
                this.token = token;
            }
        }

        public string ConsultaUsuario(string url)
        {
            var request = (HttpWebRequest)WebRequest.Create(url);
            request.ContentType = "application/json";
            request.Method = "POST";

            using (var streamWriter = new StreamWriter(request.GetRequestStream()))
            {
                string json = new JavaScriptSerializer().Serialize(new
                {
                    username = "si",
                    password = "qZ"
                });

                streamWriter.Write(json);
            }

            var response = (HttpWebResponse)request.GetResponse();
            using (var streamReader = new StreamReader(response.GetResponseStream()))
            {
                string dados = streamReader.ReadToEnd();
                return streamReader.ReadToEnd();
            }

        }