using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var guid1 = Guid.NewGuid();

        var guid2 = Guid.NewGuid();

        // Create two different lists with the same contents and a third with the same contents in a different order

        var seriesIds1 = new List<Guid> { guid1, guid2 };

        var seriesIds2 = new List<Guid> { guid1, guid2 };

        var seriesIds3 = new List<Guid> { guid2, guid1 };

        // Test the current approach

        Console.WriteLine(CurrentApproach(seriesIds1));

        Console.WriteLine(CurrentApproach(seriesIds2));

        Console.WriteLine(CurrentApproach(seriesIds3));

        // Test the other approach

        Console.WriteLine(HashSetHashCode(seriesIds1));

        Console.WriteLine(HashSetHashCode(seriesIds2));

        Console.WriteLine(HashSetHashCode(seriesIds3));

    }

    public static int CurrentApproach(List<Guid> seriesIds)

    {

        var seriesIdsHash = seriesIds.Distinct()

                .Select(item => item.GetHashCode())

                .Aggregate((total, nextCode) => total ^ nextCode);

        return seriesIdsHash;

    }

    public static int HashSetHashCode(List<Guid> seriesIds)

    {

        var seriesIdsHash = new HashSet<Guid>(seriesIds).GetHashCode();

        return seriesIdsHash;

    }

}