using System;

using System.IO;

using Newtonsoft.Json;

​

public class Program

{

    public static void Main()

    {

        string label = @"{""created_time"":""2020-04-24T16:32:45+0000"",""id"":""1872228566245481"",""field_data"":[{""name"":""email"",""values"":[""hanyeuan\u0040yahoo.com""]},{""name"":""full_name"",""values"":[""\u003CChak HY>>@Doraemon<ABC>""]},{""name"":""phone_number"",""values"":[""+60129892558""]}]}";

        if(label.Contains(">"))

        {

            label = label.Replace(">", "\\u003E");

        }

        var sr = new StringWriter();

        var jsonWriter = new JsonTextWriter(sr) {

            StringEscapeHandling =  StringEscapeHandling.Default

        };

        new JsonSerializer().Serialize(jsonWriter, label);

        //label = label.Replace(">", "\\u003E");

        Console.Out.WriteLine("1:" + label);

        Console.Out.WriteLine("2:" + sr.ToString());

    }

}