Login (JSON)

   string url = serviceUrl + "rest/login";
            string responseString = null;

            //string contentType = "application/x-www-form-urlencoded";
            //string postData = "UserName=" + accountID + "&Password=" + password;


            string contentType = null;
            string postData = null;

            if (radioBtnJson.Checked)
            {
                contentType = "text/json";//or application/json
                postData = "{\"UserName\":\"" + accountID + "\",\"Password\":\"" + password + "\"}";
                responseString = CallService(url, postData, contentType);

                //Parse login result
                JavaScriptSerializer json = new JavaScriptSerializer();
                Dictionary data = json.Deserialize>(responseString);

                if ((string)data["Message"] == "Success")
                {
                    this.key = (string)data["Key"];
                }

                // There is another way to deserialize login result.
                // We can create object LoginResult and pass as generic type in json.Deserialize<>() method.
                // For example:  LoginResult result = json.Deserialize(responseString);
                // and then we can use properties of the result variable:
                // if(result.Status=="Success")
                // {
                //      this.key = result.Key;        
                // }