using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<int> list1 = new List<int>() {1,2,3};

        List<int> list2 = new List<int>() {1,2,3};

        var result = list1.Select(x => x);

​

        // Appened to the _same_ list.

        list1.Add(12);

​

        // Prints: 1, 2, 3, 12.

        foreach (var item in result)

        {

            Console.WriteLine(item);

        }

        Console.WriteLine("----");

        // Results are enumerated, in this scenario.

        var result2 = list2.Select(x => x).ToList();

        // Appending to the list has no impact on result2, because it's been enumerated.

        list2.Add(69);

        // Prints: 1, 2, 3

        foreach (var item in result2)

        {

            Console.WriteLine(item);

        }

    }

}