Unity 2017.1 use JsonUtility decode Json String , appear "JSON must represent an object type"

Unity Engine
1

I use ASP.NET WebAPI to provide the data getting. But when I get data in Unity by www, it appears the error message “JSON must represent an object type”.

If I test directly the raw Json string , the json string is transferred to be UserTables.
Does somebody know how to solve this problem?

Raw Json String ==> UserTables successfully

        string str = "{\"Id\":1,\"UserID\":\"1\",\"UserName\":\"name1\",\"LoginType\":\"facebook  \",\"email\":\"a@a\",\"Coin\":12,\"GameNoryaKey\":\"K1\"}";
        UserTables usertable = DoSomethingWithTheCoroutineResult(str);

ASP.NET WebAPI Controller

       // GET api/values/1
        public string Get(string id)
        {
            using (DatabaseAKStudioEntities context = new DatabaseAKStudioEntities())
            {
                UserTables usertable = context.UserTables.First(a => a.UserID == id);

                string yourJson = Newtonsoft.Json.JsonConvert.SerializeObject(usertable);
                return yourJson;
            }
        }

My complete Unity C# code as below:

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class DemoService : MonoBehaviour
{
    [System.Serializable]
    public class UserTables
    {
        public int Id { get; set; }
        public string UserID { get; set; }
        public string UserName { get; set; }
        public string LoginType { get; set; }
        public string email { get; set; }
        public int Coin { get; set; }
        public string GameNoryaKey { get; set; }
    }

    void Start()
    {
        string url = "http://localhost/AKAPI/api/values/1";
        WWW www = new WWW(url);
        //string str = "{\"Id\":1,\"UserID\":\"1\",\"UserName\":\"name1\",\"LoginType\":\"facebook  \",\"email\":\"a@a\",\"Coin\":12,\"GameNoryaKey\":\"K1\"}";
        //UserTables usertable = DoSomethingWithTheCoroutineResult(str);

        StartCoroutine(WaitForRequest(www));
    }

    IEnumerator WaitForRequest(WWW www)
    {
        yield return www;

        // check for errors
        if (www.error == null)
        {
            string str = www.text;
            UserTables usertable = DoSomethingWithTheCoroutineResult(str);

            Debug.Log("WWW Result!: " + www.text);// contains all the data sent from the server
        }
        else
        {
            Debug.Log("WWW Error: " + www.error);
        }
    }

    public UserTables DoSomethingWithTheCoroutineResult(string result)
    {
        try
        {
            DemoService.UserTables usertable = JsonUtility.FromJson<DemoService.UserTables>(result);
            return usertable;
        }
        catch(Exception ex)
        {
            print(ex.Message);
        }

        return null;
    }

    // Update is called once per frame
    void Update()
    {

    }
}
2

I discover the www.text I get as below:
“"{\"Id\":1,\"UserID\":\"1\",\"UserName\":\"name1\",\"LoginType\":\"facebook \",\"email\":\"a@a\",\"Coin\":12,\"GameNoryaKey\":\"K1\"}"”

The format see to be some kind problem.

3

I had solved this problem.

        // GET /api/values/1
        public HttpResponseMessage Get(int id)
        {
            using (DatabaseAKStudioEntities context = new DatabaseAKStudioEntities())
            {
                UserTable usertable = context.UserTables.First(a => a.UserID == id.ToString());

                string yourJson = Newtonsoft.Json.JsonConvert.SerializeObject(usertable);

                var response = this.Request.CreateResponse(HttpStatusCode.OK);
                response.Content = new StringContent(yourJson, Encoding.UTF8, "application/json");

                return response;
            }
        }