c# 获取一年中的周/根据一年中的第几周获取该周的开始日期与结束日期

 /// <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));
        }