	/// <summary>
        /// ǩ
        /// </summary>
        /// <param name="parms"></param>
        /// <param name="queryString"></param>
        /// <returns>ǩַ</returns>
        private string BuildSign(NameValueCollection parms, out string queryString)
        {
            queryString = "";
            string[] keys = parms.AllKeys;
            ArrayList al = new ArrayList();
            Array.Sort(keys);

            foreach (string a in keys)
            {
                if (!string.IsNullOrEmpty(queryString)) queryString += "&";
                queryString += $"{a}=" + (string.IsNullOrEmpty(parms[a]) ? "" : HttpUtility.UrlEncode(parms[a]));
                al.Add($"{a}={parms[a]}");
            }

            return EncryptHelper.MD5Encode(ApiSecret + string.Join("&", al.ToArray()).ToLower());
        }