using System;

using Newtonsoft.Json;

using System.Collections.Generic;

public class Program

{   

    public static void Main()

    {

        var list = new List<object>();

        var obj1 = new Class1();

        obj1.Prop1 = "Pelle";

        obj1.Prop2 = "Test123";

        var obj2 = new Class2();

        obj2.Prop3 = 12;

        obj2.Prop4 = true;

        obj2.Name = "Greger";

        list.Add(obj1);

        list.Add(obj2);

        var json = JsonConvert.SerializeObject(list);

        Console.WriteLine(json);

    }

}

​

public class Class1

{

    public string Prop1 {get;set;}

    public string Prop2 {get;set;}

}

​

public class Class2

{

    public int Prop3 {get;set;}

    public bool Prop4 {get;set;}

    public string Name {get;set;}

}