GetHashcode unique? I don't think so...

UglyHash.cs

internal class Program
{
    private static void Main(string[] args)
    {
        Console.WriteLine("Hello, World!");

        HashSet<NastyEquals> uglyHash = new HashSet<NastyEquals>();

        var myHash = new NastyEquals();

        for (int i = 0; i < 10; i++)
        {
            uglyHash.Add(new NastyEquals());
        }

        uglyHash.Add(myHash);

        Console.WriteLine("Contains: {0}", uglyHash.Contains(myHash));
    }
}

internal class NastyEquals
{
    private Guid internalId;

    public NastyEquals()
    {
        internalId = Guid.NewGuid();
    }

    public override bool Equals(object? obj)
    {
        if (obj == null) return false;
        if (obj.GetType() != typeof(NastyEquals)) return false;

        Console.WriteLine($"Called: NastyEquals.Equals on object {internalId}");
        return (((NastyEquals)obj).internalId == internalId);
    }

    public override int GetHashCode()
    {
        Console.WriteLine("Called: NastyEquals.GetHashCode");
        // Just mess this up.
        return 1;
    }
}