DotNet Soundex Function

Question

I have a database table that has a column of SQLServer Soundex encoded last name + first name. In my C# program I would like to convert a string using soundex for use in my

Answer 1

Based on the answer of Dotnet Services and tigrou, I have corrected the algorithm in order to reflect the function described in Wikipedia.

Test cases such as Ashcraft = A226, Tymczak = T522, Pfister = P236 and Honeyman = H555 are now working correctly.

public static string Soundex(string data)
{
    StringBuilder result = new StringBuilder();

    if (data != null && data.Length > 0)
    {
        string previousCode = "", currentCode = "", currentLetter = "";
        result.Append(data[0]); // keep initial char

        for (int i = 0; i < data.Length; i++) //start at 0 in order to correctly encode "Pf..."
        {
            currentLetter = data[i].ToString().ToLower();
            currentCode = "";

            if ("bfpv".Contains(currentLetter)) 
                currentCode = "1";
            else if ("cgjkqsxz".Contains(currentLetter))
                currentCode = "2";
            else if ("dt".Contains(currentLetter))
                currentCode = "3";
            else if (currentLetter == "l")
                currentCode = "4";
            else if ("mn".Contains(currentLetter))
                currentCode = "5";
            else if (currentLetter == "r")
                currentCode = "6";

            if (currentCode != previousCode && i > 0) // do not add first code to result string
                result.Append(currentCode);

            if (result.Length == 4) break;

            previousCode = currentCode; // always retain previous code, even empty
        }
    }
    if (result.Length < 4)
        result.Append(new String('0', 4 - result.Length));

    return result.ToString().ToUpper();
}