/// <summary>

        /// 根据指定时间段计算工作日天数

        /// </summary>

        /// <param name="firstDay"></param>

        /// <param name="lastDay"></param>

        /// <param name="bankHolidays"></param>

        /// <returns></returns>

        public static int BusinessDaysUntil(DateTime firstDay, DateTime lastDay, params DateTime[] bankHolidays)

        {

            firstDay = firstDay.Date;

            lastDay = lastDay.Date;

            if (firstDay > lastDay)

                throw new ArgumentException("最后一天不正确" + lastDay);

            TimeSpan span = lastDay - firstDay;

            int businessDays = span.Days + ;

            int fullWeekCount = businessDays / ;

            if (businessDays > fullWeekCount * )

            {

                int firstDayOfWeek = firstDay.DayOfWeek == DayOfWeek.Sunday ?  : (int)firstDay.DayOfWeek;

                int lastDayOfWeek = lastDay.DayOfWeek == DayOfWeek.Sunday ?  : (int)lastDay.DayOfWeek;

                if (lastDayOfWeek < firstDayOfWeek)

                    lastDayOfWeek += ;

                if (firstDayOfWeek <= )

                {

                    if (lastDayOfWeek >= )

                        businessDays -= ;

                    else if (lastDayOfWeek >= )

                        businessDays -= ;

                }

                else if (firstDayOfWeek <=  && lastDayOfWeek >= )

                    businessDays -= ;

            }

            businessDays -= fullWeekCount + fullWeekCount;

            foreach (DateTime bankHoliday in bankHolidays)

            {

                DateTime bh = bankHoliday.Date;

                if (firstDay <= bh && bh <= lastDay)

                    --businessDays;

            }

            return businessDays;

        }