?????????????? ?//如本年度銷售額、本季度利潤、本月新增客戶
??????????????? //C#里內置的DateTime基本上都可以實現這些功能，巧用DateTime會使你處理這些事來變輕松多了
??????????????
??????????????? //今天
??????????????? DateTime.Now.Date.ToShortDateString();
??????????????? //昨天，就是今天的日期減一
??????????????? DateTime.Now.AddDays(-1).ToShortDateString();
??????????????? //明天，同理，加一
??????????????? DateTime.Now.AddDays(1).ToShortDateString();

??????????????? //本周(要知道本周的第一天就得先知道今天是星期幾，從而得知本周的第一天就是幾天前的那一天，要注意的是這里的每一周是從周日始至周六止
??????????????? DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
??????????????? DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
??????????????? //如果你還不明白，再看一下中文顯示星期幾的方法就應該懂了
??????????????? //由于DayOfWeek返回的是數字的星期幾，我們要把它轉換成漢字方便我們閱讀，有些人可能會用switch來一個一個地對照，其實不用那么麻煩的?????????????
??????????????? string[] Day = new string[] { "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
??????????????? Day[Convert.ToInt16(DateTime.Now.DayOfWeek)];

??????????????? //上周，同理，一個周是7天，上周就是本周再減去7天，下周也是一樣
??????????????? DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
??????????????? DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
??????????????? //下周
??????????????? DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
??????????????? DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
??????????????? //本月,很多人都會說本月的第一天嘛肯定是1號，最后一天就是下個月一號再減一天。當然這是對的
??????????????? //一般的寫法
??????????????? DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1"; //第一天
??????????????? DateTime.Parse(DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1").AddMonths(1).AddDays(-1).ToShortDateString();//最后一天

??????????????? //巧用C#里ToString的字符格式化更簡便
??????????????? DateTime.Now.ToString("yyyy-MM-01");
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();

??????????????? //上個月，減去一個月份
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString();
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
??????????????? //下個月，加去一個月份
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString();
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString();
??????????????? //7天后
??????????????? DateTime.Now.Date.ToShortDateString();
??????????????? DateTime.Now.AddDays(7).ToShortDateString();
??????????????? //7天前
??????????????? DateTime.Now.AddDays(-7).ToShortDateString();
??????????????? DateTime.Now.Date.ToShortDateString();

??????????????? //本年度，用ToString的字符格式化我們也很容易地算出本年度的第一天和最后一天
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString();
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
??????????????? //上年度，不用再解釋了吧
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString();
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString();
??????????????? //下年度
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString();
??????????????? DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString();

??????????????? //本季度，很多人都會覺得這里難點，需要寫個長長的過程來判斷。其實不用的，我們都知道一年四個季度，一個季度三個月
??????????????? //首先我們先把日期推到本季度第一個月，然后這個月的第一天就是本季度的第一天了
??????????????? DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
??????????????? //同理，本季度的最后一天就是下季度的第一天減一
??????????????? DateTime.Parse(DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
??????????????? //下季度，相信你們都知道了。。。。收工
??????????????? DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
??????????????? DateTime.Parse(DateTime.Now.AddMonths(6 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
??????????????? //上季度
??????????????? DateTime.Now.AddMonths(-3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
??????????????? DateTime.Parse(DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();

轉載于:https://www.cnblogs.com/cryloo/archive/2008/11/12/1332188.html

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