ConverterDictionary.cs

/**
 * changeCase now uses converter Dictionary
 *   If a converter is found, it invokes it
 *   or else returns null
 */
public string changeCase(string caseType, params string[] words)
{
    // Sanitize the input
    caseType = caseType.Trim().ToLower();

    // Lookup the converter function in dictonary
    ConverterFunction converter;
    converters.TryGetValue(caseType, out converter);
    if (converter !=null)
        return converter(words);
    return null;
}