using System;

using System.Collections.Generic;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        List<User> users = new List<User>();

        users.Add(new User { Id1 = 1, Id2 = 2 });

        users.Add(new User { Id1 = 3, Id2 = 4 });

        JArray array = new JArray();

        foreach (User user in users)

        {

            JObject userObj = new JObject();

            userObj.Add("Id1", user.Id1);

            userObj.Add("Id2", user.Id2);

            array.Add(userObj);

        }

        JObject result = new JObject();

        result.Add("Users", array);

        Console.WriteLine(result.ToString());

    }

}

​

class User

{

    public int Id1 { get; set; }

    public int Id2 { get; set; }

}

​