Distinct a list of strings ignoring diacritics and cases

Distinct.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace UnicodeDistinct
{
    public class Program
    {
        #region Comparers
        class LengthHash : IEqualityComparer<string>
        {
            public bool Equals(string x, string y)
            {
                if (x == null || y == null) return x == y;

                var xt = x.Trim();
                var yt = y.Trim();
                
                return xt.Length == yt.Length && Culture.CompareInfo.IndexOf(xt, yt, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase) >= 0;
            }

            public int GetHashCode(string obj) => obj?.Trim().Length ?? 1;
        }

        class IgnoreHash : IEqualityComparer<string>
        {
            public bool Equals(string x, string y)
            {
                if (x == null || y == null) return x == y;

                var xt = x.Trim();
                var yt = y.Trim();

                return xt.Length == yt.Length && Culture.CompareInfo.IndexOf(xt, yt, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase) >= 0;
            }

            public int GetHashCode(string obj) => 1;
        }

        class NormalizedHash : IEqualityComparer<string>
        {
            public bool Equals(string x, string y)
            {
                if (x == null || y == null) return x == y;

                var xt = x.Trim();
                var yt = y.Trim();

                return xt.Length == yt.Length && Culture.CompareInfo.IndexOf(xt, yt, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase) >= 0;
            }

            public int GetHashCode(string obj) => obj?.Trim().Normalize().ToUpperInvariant().GetHashCode() ?? 1;
        }
        #endregion

        #region Benchmarks
        [Benchmark]
        public List<String> RunDefault() => Itens.Distinct().ToList();

        [Benchmark]
        public List<String> RunHashAsLength() => Itens.Distinct(new LengthHash()).ToList();

        [Benchmark]
        public List<String> RunIgnoreHash() => Itens.Distinct(new IgnoreHash()).ToList();

        [Benchmark]
        public List<String> RunNormalizedHash() => Itens.Distinct(new NormalizedHash()).ToList();
        
        [Benchmark]
        public List<String> RunTrimAndCompareWithStringComparer() => Itens.Select(c => c?.Trim()).Distinct(StringComparer.InvariantCultureIgnoreCase).ToList();
        #endregion

        static CultureInfo Culture = CultureInfo.CurrentCulture;

        static readonly string[] Itens = new string[] { "hi", " hi   ", "HI", "hí", " Hî", "hi hi", " hí hí ", "olá", "OLÁ", " olá   ", "", "ola", "hola", " holà    ", "aaaa", "áâàa", " aâàa     ", "áaàa", "áâaa ", "aaaa ", "áâaa", "áâaa", };

        static void Main(string[] args)
        {
            BenchmarkRunner.Run<Program>();

            var p = new Program();
            Console.WriteLine($"{p.RunDefault().Count} Default: {string.Join(", ", p.RunDefault())}");
            Console.WriteLine($"{p.RunHashAsLength().Count} HashAsLength: {string.Join(", ", p.RunHashAsLength())}");
            Console.WriteLine($"{p.RunIgnoreHash().Count} IgnoreHash: {string.Join(", ", p.RunIgnoreHash())}");
            Console.WriteLine($"{p.RunNormalizedHash().Count} NormalizedHash: {string.Join(", ", p.RunNormalizedHash())}");
            Console.WriteLine($"{p.RunTrimAndCompareWithStringComparer().Count} RunTrimAndCompareWithStringComparer: {string.Join(", ", p.RunTrimAndCompareWithStringComparer())}");

            Console.ReadLine();
        }
    }
}