//定義變數 

        private static DateTime currentDateTime;        //當前時間
        private static DateTime lastDateTime;           //昨天時間
        private static DateTime nextDateTime;           //明天時間

        private static int currentDayOfWeek;            //今天星期幾
        private static int lastDayOfWeek;               //昨天星期幾
        private static int nextDayOfWeek;               //明天星期幾

        private static DateTime currentStartWeek;       //本週週一
        private static DateTime currentEndWeek;         //本週週日
        private static DateTime currentStartMonth;      //本月月初
        private static DateTime currentEndMonth;        //本月月末
        private static DateTime currentStartQuarter;    //本季度初
        private static DateTime currentEndQuarter;      //本季度末
        private static DateTime currentStartYear;       //今年年初
        private static DateTime currentEndYear;         //今年年末

        private static DateTime lastStartWeek;          //上週週一
        private static DateTime lastEndWeek;            //上週週日
        private static DateTime lastStartMonth;         //上月月初
        private static DateTime lastEndMonth;           //上月月末
        private static DateTime lastStartQuarter;       //上季度初
        private static DateTime lastEndQuarter;         //上季度末
        private static DateTime lastStartYear;          //去年年初
        private static DateTime lastEndYear;            //去年年末

        private static DateTime nextStartWeek;          //下週週一
        private static DateTime nextEndWeek;            //下週週日
        private static DateTime nextStartMonth;         //下月月初
        private static DateTime nextEndMonth;           //下月月末
        private static DateTime nextStartQuarter;       //下季度初
        private static DateTime nextEndQuarter;         //下季度末
        private static DateTime nextStartYear;          //明年年初
        private static DateTime nextEndYear;            //明年年末

//計算變數

            currentDateTime = DateTime.Now;                 //當前時間
            lastDateTime = DateTime.Now.AddDays(-1);        //昨天時間
            nextDateTime = DateTime.Now.AddDays(1);         //明天時間

            currentDayOfWeek = Convert.ToInt32(currentDateTime.DayOfWeek.ToString("d"));    //今天星期幾
            currentDayOfWeek = Convert.ToInt32(lastDateTime.DayOfWeek.ToString("d"));       //昨天星期幾
            currentDayOfWeek = Convert.ToInt32(nextDateTime.DayOfWeek.ToString("d"));       //明天星期幾

            currentStartWeek = currentDateTime.AddDays(1 - ((currentDayOfWeek == 0) ? 7 : currentDayOfWeek));   //本週週一
            currentEndWeek = currentStartWeek.AddDays(6);                                                       //本週週日           
            lastStartWeek = currentStartWeek.AddDays(-7);       //上週週一
            lastEndWeek = currentEndWeek.AddDays(-7);           //上週週日
            nextStartWeek = currentStartWeek.AddDays(7);        //下週週一
            nextEndWeek = currentEndWeek.AddDays(7);            //下週週日

            currentStartMonth = currentDateTime.AddDays(1 - currentDateTime.Day);   //本月月初
            currentEndMonth = currentStartMonth.AddMonths(1).AddDays(-1);           //本月月末
            lastStartMonth = currentStartMonth.AddMonths(-1);       //上月月初
            lastEndMonth = currentStartMonth.AddDays(-1);           //上月月末
            nextStartMonth = currentEndMonth.AddDays(1);            //下月月初
            nextEndMonth = nextStartMonth.AddMonths(1).AddDays(-1); //下月月末

            currentStartQuarter = currentDateTime.AddMonths(0 - (currentDateTime.Month - 1) % 3).AddDays(1 - currentDateTime.Day);  //本季度初
            currentEndQuarter = currentStartQuarter.AddMonths(3).AddDays(-1);                                                      //本季度末
            lastStartQuarter = currentStartQuarter.AddMonths(-3);           //上季度初
            lastEndQuarter = currentStartQuarter.AddDays(-1);               //上季度末
            nextStartQuarter = currentEndQuarter.AddDays(1);                //下季度初
            nextEndQuarter = nextStartQuarter.AddMonths(3).AddDays(-1);     //下季度末

            //年度運算
            currentStartYear = new DateTime(currentDateTime.Year, 1, 1);  //今年年初
            currentEndYear = new DateTime(currentDateTime.Year, 12, 31);  //今年年末
            lastStartYear = currentStartYear.AddYears(-1);  //去年年初
            lastEndYear = currentEndYear.AddYears(-1);      //去年年末
            nextStartYear = currentStartYear.AddYears(1);   //明年年初
            nextEndYear = currentEndYear.AddYears(1);       //明年年末

        /// <summary>
        /// 返回星期幾字串函式
        /// </summary>
        /// <param name="myDateTime"></param>
        /// <returns></returns>

        private string GetWeekDayName(DateTime myDateTime)
        {
            string week = "";
            //獲取當前日期是星期幾
            string dt = myDateTime.DayOfWeek.ToString();
            //根據取得的星期英文單詞返回漢字
            switch (dt)
            {
                case "Monday":
                    week = "星期一";
                    break;
                case "Tuesday":
                    week = "星期二";
                    break;
                case "Wednesday":
                    week = "星期三";
                    break;
                case "Thursday":
                    week = "星期四";
                    break;
                case "Friday":
                    week = "星期五";
                    break;
                case "Saturday":
                    week = "星期六";
                    break;
                case "Sunday":
                    week = "星期日";
                    break;
            }
            return week;
        }