using System;

using Newtonsoft.Json;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        //create list

        List<Entity1> list1 = new List<Entity1>();

        List<Entity2> list2 = new List<Entity2>();

        //adding some values

        Entity1 e1 = new Entity1{

            Name = "Can",

            Surname="Cmrt"

        };

        Entity1 e2 = new Entity1{

            Name = "Arya",

            Surname="Stark"

        };

        Entity1 e3 = new Entity1{

            Name = "John",

            Surname="Snow"

        };

        Entity2 classroom = new Entity2{

            Classroom = "1-A"

        };

        list1.Add(e1);

        list1.Add(e2);

        list1.Add(e3);

        list2.Add(classroom);

        List<object> objList = new List<object>();

        objList.Add(list1);

        objList.Add(list2);

        string arrayOfObjects = JsonConvert.SerializeObject();

        Console.WriteLine(arrayOfObjects);

    }

}

public class Entity1{

        public string Name {get;set;}

        public string Surname{get;set;}

}

public class Entity2{

        public string Classroom {get;set;}

}