C# Md5Hash

/// <summary>
        /// MD5　32位加密(大寫)
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        static string UserMd5(string str)
        {
            string cl = str;
            string pwd = "";
            MD5 md5 = MD5.Create();//實例化一個md5對像
            // 加密後是一個位元組類型的數組，這裡要註意編碼UTF8/Unicode等的選擇　
            byte[] s = md5.ComputeHash(Encoding.UTF8.GetBytes(cl));
            // 通過使用迴圈，將位元組類型的數組轉換為字元串，此字元串是常規字元格式化所得
            for (int i = 0; i < s.Length; i++)
            {
                // 將得到的字元串使用十六進位類型格式。格式後的字元是小寫的字母，如果使用大寫（X）則格式後的字元是大寫字元 

                pwd = pwd + s[i].ToString("X");

            }
            return pwd;
        }
        /// <summary>
        /// MD5 16位加密 加密後密碼為小寫
        /// </summary>
        /// <param name="ConvertString"></param>
        /// <returns></returns>
        public static string GetMd5str(string ConvertString)
        {
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(ConvertString)), 4, 8);
            t2 = t2.Replace("-", "");
            t2 = t2.ToLower();
            return t2;
        }
        /// <summary>
        /// MD5 16位加密 加密後密碼為大寫
        /// </summary>
        /// <param name="ConvertString"></param>
        /// <returns></returns>
        public static string GetMd5Str(string ConvertString)
        {
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
            string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(ConvertString)), 4, 8);
            t2 = t2.Replace("-", "");
            return t2;
        }
        /// <summary>
        /// MD5加密(小寫)
        /// </summary>
        /// <param name="input"></param>
        /// <returns></returns>
        private static string Md5Hash(string input)
        {
            MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider();
            byte[] data = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input));
            StringBuilder sBuilder = new StringBuilder();
            for (int i = 0; i < data.Length; i++)
            {
                sBuilder.Append(data[i].ToString("x2"));
            }
            return sBuilder.ToString();
        }