testing DT Serialization, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Newtonsoft.Json;

namespace Rextester
{
    public class Program
    {
        public class obj
        {
            public int Id { get; set; }
        public object Answer { get; set; }
        }
        public class str
        {
            public int Id { get; set; }
            public string Answer { get; set; }
        }
        
        public static void Main(string[] args)
        {            
            var dtString = "17.08.2017 15:20:24";
                        
            var l1 = new List<obj>{ new obj{Id = 1, Answer = DateTime.Now}};
            var l2 = new List<obj>{ new obj{Id = 1, Answer = DateTime.Now.ToString()}};
            var l3 = new List<obj>{ new obj{Id = 1, Answer = dtString}};
            var l4 = new List<obj>{ new obj{Id = 1, Answer = DateTime.Parse(dtString)}};
            
            var l6 = new List<str>{ new str{Id = 1, Answer = DateTime.Now.ToString()}};
            var l7 = new List<str>{ new str{Id = 1, Answer = dtString}};
            var l9 = new List<str>{ new str{Id = 1, Answer = DateTime.Parse(dtString).ToString()}};
                        
            
            Console.WriteLine(JsonConvert.SerializeObject(l1));
            Console.WriteLine(JsonConvert.SerializeObject(l2));
            Console.WriteLine(JsonConvert.SerializeObject(l3));
            Console.WriteLine(JsonConvert.SerializeObject(l4));
            Console.WriteLine(JsonConvert.SerializeObject(l6));
            Console.WriteLine(JsonConvert.SerializeObject(l7));
            Console.WriteLine(JsonConvert.SerializeObject(l9));
            
            
            //Your code goes here
            Console.WriteLine("Hello, world!");
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0,14 sec, absolute running time: 0,34 sec, cpu time: 0,34 sec, average memory usage: 23 Mb, average nr of threads: 5