显示日期是当前区间第几周？

 

        /// <summary>
        /// 显示日期是当前区间第几周？
         /// </summary>
        /// <param name="day">当前日期</param>
        /// <param name="datespanGuid"></param>
        /// <returns></returns>
        public int GetCurrentWeek(DateTime day, Guid datespanGuid) 
        {
            CDateSpan span = db.CDateSpan.SingleOrDefault(u => u.DateSpanGuid == datespanGuid);
            if (span != null && span.EndTime.Subtract(day).Days >= 0 && day.Subtract(span.BeginTime).Days >= 0)
            {
                int currentWeek = 1;

                //计算出第一周周末（星期六）的日期
                DateTime beginSaturday = span.BeginTime.Add(new TimeSpan(span.Offset, 0, 0, 0));    //span.BeginTime-span.Offset：起始周开始计算的时间

                int saturdaySpan = 6 - (int)(beginSaturday.DayOfWeek);    //这天离周末还有几天

                beginSaturday = beginSaturday.Add(new TimeSpan(saturdaySpan, 0, 0, 0)); // 周末的日期

                //
                int days = day.Subtract(beginSaturday).Days;
                if (days > 0) 
                {
                    currentWeek += days / 7 + 1;
                }
               
                return currentWeek;
            }
            else 
            {
                return -1;//区间不存在或者日期不在区间中
            }
        }