计算工作日

        public static DateTime GetWorkday(DateTime now, int days)
        {
            int week = (int)now.DayOfWeek;
            int addday = days / 5 * 7 + days % 5;
            if (week == 6)//如果是周六就加一天到星期天
            {
                addday += 1;
            }
            else if ((week + days % 5) > 5)
            {
                addday += 2;
            }
            return now.AddDays(addday);
        }

        public static DateTime GetWorkdayLoop(DateTime now, int days)
        {
            DateTime temp = now;
            while (days-- > 0)
            {
                temp = temp.AddDays(1);
                while (temp.DayOfWeek == System.DayOfWeek.Saturday || temp.DayOfWeek == System.DayOfWeek.Sunday)
                    temp = temp.AddDays(1);
            }
            return temp;
        }