C#获取本周第一天和最后一天

            DateTime nowTime = DateTime.Now;
            #region 获取本周第一天
            //星期一为第一天  
            int weeknow = Convert.ToInt32(nowTime.DayOfWeek);

            //因为是以星期一为第一天，所以要判断weeknow等于0时，要向前推6天。  
            weeknow = (weeknow == 0 ? (7 - 1) : (weeknow - 1));
            int daydiff = (-1) * weeknow;

            //本周第一天  
            DateTime FirstDay = nowTime.AddDays(daydiff);
　　　　　　  #endregion

            #region 获取本周最后一天
            //星期天为最后一天  
            int lastWeekDay = Convert.ToInt32(nowTime.DayOfWeek);
            lastWeekDay = lastWeekDay == 0 ? (7 - lastWeekDay) : lastWeekDay;
            int lastWeekDiff = (7 - lastWeekDay);

            //本周最后一天  
            DateTime LastDay = nowTime.AddDays(lastWeekDiff);

　　　　　　  #endregion