自动生成随机数

        /// <summary>
        /// 取得随机数
        /// </summary>
        /// <param name="randnumlength">随机数位数</param>
        /// <returns></returns>
        public static string getrandnum(int randnumlength)
        {
            System.Random randnum = new System.Random(unchecked((int)DateTime.Now.Ticks));
            string str = "";
            for (int i = 0; i < randnumlength; i++)
            {
                str = str + randnum.Next(0, 9);
            }
            return str;
        }