代码之家 › 专栏 › 技术社区 › Henryk

计算前一周的开始和结束日期

Henryk · 技术社区 · 16 年前

用C#计算前一周开始和结束日期的最佳方法是什么?即今天3月18日将导致3月9日(上周星期一)和3月15日(上周星期日)。

我已经看到用DayOfWeek和switch语句来计算偏移量,但我想知道是否有更优雅的方法。

7 回复 | 直到 16 年前

bstoney 16 年前

您可以跳过while循环并使用

DateTime mondayOfLastWeek = date.AddDays( -(int)date.DayOfWeek - 6 );

mqp 16 年前

DayOfWeek weekStart = DayOfWeek.Monday; // or Sunday, or whenever
DateTime startingDate = DateTime.Today;

while(startingDate.DayOfWeek != weekStart)
    startingDate = startingDate.AddDays(-1);

DateTime previousWeekStart = startingDate.AddDays(-7);
DateTime previousWeekEnd = startingDate.AddDays(-1);

阅读:一次回顾一天,直到本周开始,然后减去7,直到上周开始。

Simon Randy Burden 11 年前

使用Fluent DateTime https://github.com/FluentDateTime/FluentDateTime

var dateTime = 1.Weeks().Ago();
var monday = dateTime.Previous(DayOfWeek.Sunday);
var sunday = dateTime.Next(DayOfWeek.Sunday);

Andy Rose 16 年前

使用DayOfWeek将是实现这一目标的一种方式:

    DateTime date = DateTime.Now.AddDays(-7);
    while (date.DayOfWeek != DayOfWeek.Monday)
    {
        date = date.AddDays(-1);
    }

    DateTime startDate = date;
    DateTime endDate = date.AddDays(7);

Martin 6 年前

当前已接受的答案将在星期天失败,因为它将给出当前星期的星期一,而不是最后一周的星期一。 (带有单元测试输出的代码)

DateTime mondayOfLastWeek = date.AddDays( -(int)date.DayOfWeek - 6 );
//Failed to get start of last-week from date-time: 2020-03-01T00:00:00.0000000Z
//  Expected: 2020-02-17 00:00:00.000
//  But was:  2020-02-24 00:00:00.000

以下代码位解决了此问题:

var dayOfWeek = (int) date.DayOfWeek - 1;
if (dayOfWeek < 0) dayOfWeek = 6;

var thisWeeksMonday = date.AddDays(-dayOfWeek).Date;
var lasWeeksMonday = thisWeeksMonday.AddDays(-7);

如果您希望,可以将其简化为一行代码(我不建议使用这种几乎不可读的代码…):

var mondayOfLastWeek  = date.AddDays(-(7 + ((int)date.DayOfWeek - 1 == -1 ? 6 : (int)date.DayOfWeek - 1)));

Matt 4 年前

您可以创建DateTime扩展方法,该方法可与DayOfWeek参数一起使用:

public static class DateTimeExtension
{
    public static DateTime GetPreviousWeekDay(this DateTime currentDate, DayOfWeek dow)
    {
        int currentDay = (int)currentDate.DayOfWeek, gotoDay = (int)dow;
        return currentDate.AddDays(-7).AddDays(gotoDay-currentDay);
    }        
}

DateTime testDate = new DateTime(2017, 01, 21);
        
Console.WriteLine(testDate.GetPreviousWeekDay(DayOfWeek.Sunday));
Console.WriteLine(testDate.GetPreviousWeekDay(DayOfWeek.Saturday));

要使用它获取从当前日期算起的前一周(如问题中所述):

var prevWkStartDate = DateTime.Now.GetPreviousWeekDay(DayOfWeek.Monday); 
var prevWkEndDate = DateTime.Now.GetPreviousWeekDay(DayOfWeek.Sunday);
Console.Write($"Previous week starts at {prevWkStartDate.ToShortDateString()}");
Console.WriteLine($" and ends at {prevWkEndDate.ToShortDateString()}");

更新:这似乎需要修复(示例日期:2020年12月10日):

public static DateTime GetPreviousWeekDay(this DateTime currentDate, DayOfWeek dow)
{
    int d = 0; if (dow == DayOfWeek.Sunday) { dow = DayOfWeek.Saturday; d = 1; }
    int currentDay = (int)currentDate.DayOfWeek, gotoDay = (int)dow;
    return currentDate.AddDays(-7).AddDays(gotoDay - currentDay + d);
}

nepdev 7 年前

当一周“中断”时,即当它考虑到一周的结束或开始,而接受的解决方案中的公式不考虑时,您必须切换。

DateTime thu = date.AddDays(-(int)(date.AddDays(-5).DayOfWeek) -1);

周一,5将切换到2。

要打印的示例代码

        String s = "";
        DateTime date = new DateTime(2017, 1, 1);
        for (int i = 0; i < 14; i++)
        {
            date = date.AddDays(1);
            DateTime thu = date.AddDays(-(int)(date.AddDays(-5).DayOfWeek) -1);
            DateTime mon = date.AddDays(-(int)(date.AddDays(-2).DayOfWeek) -1);
            s += date.ToString() + " - Thu: " + thu.ToString() + " - Mon: " + mon.ToString() + "\r\n";
        }
        Console.WriteLine(s);