using System;

using System.Collections.Generic;

using System.Linq;

using System.Dynamic;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        int[,] myArr = {

            {1, 2},

            {3, 4}

        };

​

        dynamic myObj = new ExpandoObject();

        var list = new List<dynamic>();

        foreach(var myInt in myArr)

        {

            list.Add( 

                new

                {

                    value = myInt,

                    value_plus_1 = myInt + 1

                }

            );

        }

        myObj.Ints = list;

        Console.WriteLine(JsonConvert.SerializeObject(myObj));

    }

}