using System;

using System.Collections.Generic;

public class Program

{

    public class Test : IEquatable<Test>

    {

        public List<int> list = new List<int> {1, 2, 3};

        public bool Equals(Test other)

        {

            list.Sort();

            other.list.Sort();

            return false;

        }

        // force a hash collision

        public override int GetHashCode() { return 1; }

    }

    public static void Main()

    {

        Test t1 = new Test();

        HashSet<Test> hashSet = new HashSet<Test> { new Test() };

        foreach(int i in t1.list)

            hashSet.Contains(t1);

    }

}