MD5签名32位

        //编码格式
        private static string inputCharset = "utf-8";

        /// <summary>
        /// 签名字符串
        /// </summary>
        /// <param name="prestr">需要签名的字符串</param>
        /// <param name="key">密钥</param>
        /// <returns>签名结果</returns>
        public static string Sign(string prestr, string key)
        {
            StringBuilder sb = new StringBuilder(32);
            prestr = prestr + key;
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] t = md5.ComputeHash(Encoding.GetEncoding(inputCharset).GetBytes(prestr));
            for (int i = 0; i < t.Length; i++)
            {
                sb.Append(t[i].ToString("x").PadLeft(2, '0'));
            }
            return sb.ToString();
        }