public static class StringUtil

    {

        /// <summary>

        /// 单词变成单数形式

        /// </summary>

        /// <param name="word"></param>

        /// <returns></returns>

        public static string ToSingular(string word)

        {

            Regex plural1 = new Regex("(?<keep>[^aeiou])ies$");

            Regex plural2 = new Regex("(?<keep>[aeiou]y)s$");

            Regex plural3 = new Regex("(?<keep>[sxzh])es$");

            Regex plural4 = new Regex("(?<keep>[^sxzhyu])s$");

            if (plural1.IsMatch(word))

                return plural1.Replace(word, "${keep}y");

            else if (plural2.IsMatch(word))

                return plural2.Replace(word, "${keep}");

            else if (plural3.IsMatch(word))

                return plural3.Replace(word, "${keep}");

            else if (plural4.IsMatch(word))

                return plural4.Replace(word, "${keep}");

            return word;

        }

        /// <summary>

        /// 单词变成复数形式

        /// </summary>

        /// <param name="word"></param>

        /// <returns></returns>

        public static string ToPlural(string word)

        {

            Regex plural1 = new Regex("(?<keep>[^aeiou])y$");

            Regex plural2 = new Regex("(?<keep>[aeiou]y)$");

            Regex plural3 = new Regex("(?<keep>[sxzh])$");

            Regex plural4 = new Regex("(?<keep>[^sxzhy])$");

            if (plural1.IsMatch(word))

                return plural1.Replace(word, "${keep}ies");

            else if (plural2.IsMatch(word))

                return plural2.Replace(word, "${keep}s");

            else if (plural3.IsMatch(word))

                return plural3.Replace(word, "${keep}es");

            else if (plural4.IsMatch(word))

                return plural4.Replace(word, "${keep}s");

            return word;

        }

    }