using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        IEnumerable<Elig> masterList = new List<Elig> { new Elig() };

​

        IEnumerable<Elig> list1 = masterList.SelectMany(x => GetSubList());

        foreach (var i in list1)

        {

            i.test = "Altered";

        }

​

        IEnumerable<Elig> list2 = masterList.SelectMany(x => GetSubList()).ToList();

        list2.First().test = "Altered";

​

        IEnumerable<Elig> list3 = masterList.SelectMany(x => new List<Elig> { new Elig { test = "Original" } });

        list3.First().test = "Altered";

​

        var subList = new List<Elig> { new Elig { test = "Original" } };

        IEnumerable<Elig> list4 = masterList.SelectMany(x => subList);

        list4.First().test = "Altered";

        IEnumerable<Elig> list5 = GetSubList().Where(x => true);

        list1.First().test = "Altered";

​

        Console.WriteLine("List1:" + string.Join(" ", list1.Select(x => x.test))); // returns "Original"

        Console.WriteLine("List2:" + string.Join(" ", list2.Select(x => x.test))); // returns "Altered"

        Console.WriteLine("List3:" + string.Join(" ", list3.Select(x => x.test))); // returns "Original"

        Console.WriteLine("List4:" + string.Join(" ", list4.Select(x => x.test))); // returns "Altered"

    }

​

    public static List<Elig> GetSubList()

    {

        return new List<Elig> { new Elig { test = "Original" } };

    }

}

​

public class Elig

{

    public string test;

}

​