/// <summary>
        /// 生成随机字符串(目前为订单编号所用)格式：yyMMdd+6位长度的随机数
        /// </summary>
        /// <returns></returns>
        public static string GenerateRandomStr()
        {
            Random rand = new Random(Guid.NewGuid().GetHashCode());
            return DateTime.Now.ToString("yyMMdd") + rand.Next(100000, 999999);
        }