ทำไม unicode แปลงกลับเป็นอักษรไทยไม่ได้ เวลา return json ทั้งๆๆที่ set เป็น toString งง ปวดหัวมากเลย

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Windows.Forms;

namespace SampleGetJson
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {           
            string json = get_web_content(url);
            dynamic array = JsonConvert.DeserializeObject(json);      
            foreach (var item in array)
            {
                docIsoList.Add(new DocIso { Id = item["Id"]
                    ,DocNum = item["doc_num"]
                ,DocDate = item["doc_date"]
                ,DocType = item["doc_type"]
                ,CustName = item["cust_name"]
                ,Nonconformity = item["nonconformity"]
                ,Job = item["job"]});
            }
            this.dataGridView1.DataSource = docIsoList;
        }
        private string url = "http://localhost/aut_datacenter/adminapi/docs";
        private List<DocIso> docIsoList = new List<DocIso>();      
        public string  get_web_content(string url)
        {
            Uri uri = new Uri(url);
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(uri);
            request.Method = WebRequestMethods.Http.Get;
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            StreamReader reader = new StreamReader(response.GetResponseStream());
            string output = reader.ReadToEnd();
            response.Close();
            return output;
        }
    }
    public class DocIso
    {        
        public String Id { get; set; }       
        public String DocNum { get; set; }       
        public String DocDate { get; set; }       
        public String DocType { get; set; }      
        public String Nonconformity { get; set; }       
        public String CustName { get; set; }      
        public String Job { get; set; }
    }
}