HttpClient

        public void UserLogin()
        {
            using (HttpClient client = new HttpClient())
            {
                client.DefaultRequestHeaders.Add("Authorization", default_Token);
                List<KeyValuePair<String, String>> paramList = new List<KeyValuePair<String, String>>();
                paramList.Add(new KeyValuePair<string, string>("grant_type", "password"));
                paramList.Add(new KeyValuePair<string, string>("activationCode", "CloudPeak"));
                paramList.Add(new KeyValuePair<string, string>("deviceId", "CloudPeak"));
                var response = client.PostAsync(serverUrl+"/OAuth/Token", new FormUrlEncodedContent(paramList)).Result;
                var str = response.Content.ReadAsStringAsync().Result;
               var aa = JObject.Parse(str).ToObject<Dictionary<string, string>>();
               string tokenstr = aa["access_token"];
               user_Token = "Bearer " + tokenstr;
               isUserLogin = true;
               //MessageBox.Show(tokenstr);
            }
        }