using System;

using System.Collections;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var list = new List<TestObject>();

        list.Add(new TestObject());

        var listb = list;

        list.Add(new TestObject());

        Console.WriteLine(list.Count); //this definitely has 2

        Console.WriteLine(listb.Count); //this also has 2 because Lists are assigned by reference, not deep copied / cloned

    }

}

​

public class TestObject

{

}