Custom benchmark code for https://twitter.com/esesci/status/1611158796814155777

RegexVsToCharArray.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Text.RegularExpressions;

namespace RegexVsToCharArray;

[MemoryDiagnoser]
public class MemoryBenchmarker
{
    static readonly string[] names = { "Plague Tale", "Callisto Protocol", "God Of War", "Street Fighter 6", "Elden Ring" };
    const string exceptList = "aeiur";

    [Benchmark]
    public IList<string> ToCharArray()
    {
        var query =
            from name in names
            where name.ToCharArray().Where(c => !exceptList.Contains(c)).Count() > 10
            select name;
        return query.ToList();
    }

    [Benchmark]
    public IList<string> Regex_Inline()
    {
        return names
            .Where(s => Regex.Replace(s, "[aeiur]+", "").Length > 10)
            .ToList();
    }

    [Benchmark]
    public IList<string> Regex_Compiled()
    {
        return names
            .Where(s => Regex.Replace(s, "[aeiur]+", "", RegexOptions.Compiled).Length > 10)
            .ToList();
    }

    [Benchmark]
    public IList<string> CustomMatch()
    {
        static bool matches(string s)
        {
            int sum = 0;
            foreach (char c in s)
            {
                if (!exceptList.Contains(c))
                {
                    sum++;
                }
                if (sum > 10)
                {
                    return true;
                }
            }
            return false;
        }

        return names.Where(s => matches(s)).ToList();
    }

    [Benchmark]
    public IList<string> TakeWhile()
    {
        return names
            .Where(s => s.TakeWhile(c => !exceptList.Contains(c)).Count() > 10)
            .ToList();
    }

    static void Main()
    {
        _ = BenchmarkRunner.Run<MemoryBenchmarker>();
    }
}