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  • C#中时间相关知识点小结

    C#中时间相关知识点小结

    一、月份英文简写

      DateTime dt = DateTime.Now;
      string MM = dt.AddMonths(-1).ToString("MMM", new System.Globalization.CultureInfo("en-us"));//月英文缩写:Jul

    二、当月第一天和最后一天

    DateTime ThisMonth_Frist = DateTime.Now.AddDays(1 - DateTime.Now.Day).Date;
    DateTime ThisMOnth_Last = DateTime.Now.AddDays(1 - DateTime.Now.Day).Date.AddMonths(1).AddSeconds(-1);

    三、上月第一天和最后一天

    DateTime Today = DateTime.Today;//当天时间
    DateTime ThisMonth = new DateTime(Today.Year, Today.Month, 1);//当前月第一天时间
    DateTime LastMonth_First = ThisMonth.AddMonths(-1);//上月第一天时间
    DateTime LastMonth_Last = ThisMonth.AddDays(-1);//上月最后一天时间

    四、本周第几天

    int daysInWeek1 = (int)DateTime.Now.DayOfWeek;//注意:此处周,日时返回0,
    int daysInWeek2 = (int)DateTime.Now.DayOfWeek == 0 ? 7 : (int)DateTime.Now.DayOfWeek;//当前周第几天,注释:周日为0

    五、本月第几周

    int a = WeekOfMonth(DateTime.Now, false);//

    六、本年第几周

         private int WeekOfYear()
            {
                var dt = DateTime.Now;
                int firstWeekend = Convert.ToInt32(DateTime.Parse(dt.Year + "-1-1").DayOfWeek);
                int weekDay = firstWeekend == 0 ? 1 : (7 - firstWeekend + 1);
                int currentDay = dt.DayOfYear;
                int current_week = Convert.ToInt32(Math.Ceiling((currentDay - weekDay) / 7.0)) + 1;
                return current_week;
            }

    七、前几周的周一和周日

     private void FEDayInLastWeek()
            {
                int N = 3;//前几周参数
                DateTime Today = DateTime.Now;
                int daysInWeek = (int)Today.DayOfWeek == 0 ? 7 : (int)Today.DayOfWeek;//当前周第几天,注释:周日为0
               
                for (int i = N; i > 0; i--)
                {
                    //起始日期
                    DateTime firstDay = Today.AddDays(1 - (7 * i + daysInWeek));
                    DateTime lastDay = Today.AddDays(7 - (7 * i + daysInWeek));
                }
            }

    八、本周一和当前日

       private void FristDayToNowInThisWeek()
            {
                int daysInWeek = (int)DateTime.Now.DayOfWeek == 0 ? 7 : (int)DateTime.Now.DayOfWeek;//当前周第几天,注释:周日为0
                //起始日期
                DateTime firstDay = DateTime.Now.AddDays(1 - daysInWeek);
                DateTime lastDay = DateTime.Now;
            }

     


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  • 原文地址:https://www.cnblogs.com/wml-it/p/14963113.html
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