using System;

using System.Linq;

using System.Text;

using System.Text.RegularExpressions;

​

// http://seesharpdeveloper.blogspot.fr/2013/07/soundex-algorithm-in-c.html

public static class Soundex

{

    public static string For(string word)

    {

        const int MaxSoundexCodeLength = 4;

        var soundexCode = new StringBuilder();

        var previousWasHOrW = false;

        word = Regex.Replace(word == null ? string.Empty : word.ToUpper(), @"[^\w\s]", string.Empty);

        if (string.IsNullOrEmpty(word))

        {

            return string.Empty.PadRight(MaxSoundexCodeLength, '0');

        }

​

        soundexCode.Append(word.First());

        for (var i = 1; i < word.Length; i++)

        {

            var numberCharForCurrentLetter = GetCharNumberForLetter(word[i]);

            if (i == 1 && numberCharForCurrentLetter == GetCharNumberForLetter(soundexCode[0]))

            {

                continue;

            }

​

            if (soundexCode.Length > 2 && previousWasHOrW && numberCharForCurrentLetter == soundexCode[soundexCode.Length - 2])

            {

                continue;

            }

​

            if (soundexCode.Length > 0 && numberCharForCurrentLetter == soundexCode[soundexCode.Length - 1])

            {

                continue;

            }

​

            soundexCode.Append(numberCharForCurrentLetter);

            previousWasHOrW = "HW".Contains(word[i]);

        }

​

        return soundexCode.Replace("0", string.Empty).ToString().PadRight(MaxSoundexCodeLength, '0').Substring(0, MaxSoundexCodeLength);

    }

​

    private static char GetCharNumberForLetter(char letter)

    {

        if ("BFPV".Contains(letter))

            return '1';

        if ("CGJKQSXZ".Contains(letter))

            return '2';

        if ("DT".Contains(letter))

            return '3';

        if ('L' == letter)

            return '4';

        if ("MN".Contains(letter))

            return '5';

        if ('R' == letter)

            return '6';

        return '0';

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Soundex.For("Cadeau"));

        Console.WriteLine(Soundex.For("kdo"));

        Console.WriteLine(Soundex.For("Michel"));

        Console.WriteLine(Soundex.For("Michèle"));

    }

}