using System;

using System.Diagnostics;

using System.Linq;

using System.Text;

using System.Text.RegularExpressions;

​

internal static class MeasureTime

{

    internal static TimeSpan Run(Action func, uint count = 1)

    {

        if (count == 0)

        {

            throw new ArgumentOutOfRangeException("count", "Must be greater than zero");

        }

​

        long[] arr_time = new long[count];

        Stopwatch sw = new Stopwatch();

        for (uint i = 0; i < count; i++)

        {

            sw.Start();

            func();

            sw.Stop();

            arr_time[i] = sw.ElapsedTicks;

            sw.Reset();

        }

​

        return new TimeSpan(count == 1 ? arr_time.Sum() : Convert.ToInt64(Math.Round(arr_time.Sum() / (double)count)));

    }

}

​

public class Program

{

    public static string RandomString(int length)

    {

        Random random = new Random();

        const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        return new String(Enumerable.Range(1, length).Select(_ => chars[random.Next(chars.Length)]).ToArray());

    }

​

    public static void Main()

    {

        string rnd_str = RandomString(500000);

        Regex regex = new Regex("a|c|e|g|i|k", RegexOptions.Compiled);

        TimeSpan ts1 = MeasureTime.Run(() => regex.Replace(rnd_str, "!!!"), 10);

        Console.WriteLine("Regex time: {0:hh\\:mm\\:ss\\:fff}", ts1);

        StringBuilder sb_str = new StringBuilder(rnd_str);

        TimeSpan ts2 = MeasureTime.Run(() => sb_str.Replace("a", "").Replace("c", "").Replace("e", "").Replace("g", "").Replace("i", "").Replace("k", ""), 10);

        Console.WriteLine("StringBuilder time: {0:hh\\:mm\\:ss\\:fff}", ts2);

        TimeSpan ts3 = MeasureTime.Run(() => rnd_str.Replace("a", "").Replace("c", "").Replace("e", "").Replace("g", "").Replace("i", "").Replace("k", ""), 10);

        Console.WriteLine("String time: {0:hh\\:mm\\:ss\\:fff}", ts3);

        char[] ch_arr = {'a', 'c', 'e', 'g', 'i', 'k'};

        TimeSpan ts4 = MeasureTime.Run(() => new String((from c in rnd_str where !ch_arr.Contains(c) select c).ToArray()), 10);

        Console.WriteLine("LINQ time: {0:hh\\:mm\\:ss\\:fff}", ts4);

    }

}