/// <summary>        /// 获取一年中的周        /// </summary>        /// <param name="dt">日期</param>        /// <returns></returns>        public static int GetWeekOfYear(DateTime dt)        {            System.Globalization.GregorianCalendar gc = new System.Globalization.GregorianCalendar();            int weekOfYear = gc.GetWeekOfYear(dt, System.Globalization.CalendarWeekRule.FirstDay, DayOfWeek.Monday);            return weekOfYear;        }        /// <summary>        /// 根据一年中的第几周获取该周的开始日期与结束日期        /// </summary>        /// <param name="year"></param>        /// <param name="weekNumber"></param>        /// <param name="culture"></param>        /// <returns></returns>        public static Tuple<DateTime, DateTime> GetFirstEndDayOfWeek(int year, int weekNumber, System.Globalization.CultureInfo culture)        {            System.Globalization.Calendar calendar = culture.Calendar;            DateTime firstOfYear = new DateTime(year, 1, 1, calendar);            DateTime targetDay = calendar.AddWeeks(firstOfYear, weekNumber-1);            DayOfWeek firstDayOfWeek = culture.DateTimeFormat.FirstDayOfWeek;            while (targetDay.DayOfWeek != firstDayOfWeek)            {                targetDay = targetDay.AddDays(-1);            }            return Tuple.Create<DateTime, DateTime>(targetDay, targetDay.AddDays(6));        }