/// <summary>
        /// 生成请求时的签名
        /// </summary>
        /// <param name="sPara">请求给支付宝的参数数组</param>
        /// <returns>签名结果</returns>
        private static string BuildRequestMysign(Dictionary <string, string> sPara)
        {
            //把数组所有元素,按照“参数=参数值”的模式用“&”字符拼接成字符串
            string prestr = Core.CreateLinkString(sPara);

            //把最终的字符串签名,获得签名结果
            string mysign = "";

            switch (_sign_type)
            {
            case "MD5":
                mysign = AlipayMD5.Sign(prestr, _key, _input_charset);
                break;

            default:
                mysign = "";
                break;
            }

            return(mysign);
        }