在 C# 中给定周数和年份计算一周的开始和结束日期（基于 ISO 规范）
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Calculate the start and end date of a week given the week number and year in C# (based on the ISO specification)
提问by
I need to generate a report that shows the 52 weeks of a year (or 53 weeks as some years have) and their start and end dates. There is an ISO spec to do this but seems awfully complicated! Im hoping someone knows of a way to do it in C# or Visual Basic (its actually for Visual Basic 6 but I will try port it across)
我需要生成一份报告，显示一年中的 52 周（或某些年份的 53 周）及其开始和结束日期。有一个 ISO 规范可以做到这一点，但看起来非常复杂！我希望有人知道在 C# 或 Visual Basic 中执行此操作的方法（它实际上适用于 Visual Basic 6，但我会尝试将其移植）
回答by Paul van Brenk
use the Calendar.GetWeekOfYearmethod to get the week of the current datetime, the rest should be trivial.
使用Calendar.GetWeekOfYear方法获取当前日期时间的星期，其余的应该是微不足道的。
For vb6 it's less trivial, you're best bet is to find a good library which does the hard work for you.
对于 vb6，它不是那么简单，你最好的办法是找到一个很好的库，它可以为你完成艰苦的工作。
回答by Matt Howells
回答by Guffa
You can use the Calendar.GetWeekOfYearmethod to get the week number of a date, with the CalendarWeekRule.FirstFourDayWeekvalue to specify how the weeks are determined, and DayOfWeek.Mondayto specify the first weekday. That follows the ISO specification.
您可以使用该Calendar.GetWeekOfYear方法获取日期的周数，该CalendarWeekRule.FirstFourDayWeek值指定周的确定方式，并DayOfWeek.Monday指定第一个工作日。这遵循 ISO 规范。
Example:
例子：
int week = Calendar.GetWeekOfYear(DateTime.Today, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday);
To get the first date of the first week of the year, you can start from the 4th of january and go back until you find the monday:
要获得一年中第一周的第一个日期，您可以从 1 月 4 日开始并返回，直到找到星期一：
DateTime t = new DateTime(DateTime.Today,Year, 1, 4);
while (t.DayOfWeek != DayOfWeek.Monday) t = t.AddDays(-1);
回答by Thorarin
This should work. I've used it on reporting in the past. I agree that it's not very pretty though:
这应该有效。我过去曾在报告中使用过它。我同意它虽然不是很漂亮：
DateTime GetWeekStartDate(int year, int week)
{
DateTime jan1 = new DateTime(year, 1, 1);
int day = (int)jan1.DayOfWeek - 1;
int delta = (day < 4 ? -day : 7 - day) + 7 * (week - 1);
return jan1.AddDays(delta);
}
That calculates the start date for a certain week. The end DateTime is obviously 7 days later (exclusive).
这会计算某一周的开始日期。结束日期时间显然是 7 天后（独家）。
You may find this code of mineuseful. It's barely documented, but it implements a few other operations on the WeekAndYear struct it defines. Plenty of room for improvement. Most notably, it defines <and >operators, but no others, which is pretty bad... but it should get you started.
你可能会发现我的这段代码很有用。它几乎没有记录，但它在它定义的 WeekAndYear 结构上实现了一些其他操作。有很大的改进空间。最值得注意的是，它定义了<和>操作符，但没有其他的，这很糟糕……但它应该让你开始。
Porting to VB6 though... Hmm, maybe not :P
虽然移植到 VB6 ......嗯，也许不是：P
回答by Thorarin
These functions covered my requirements (adapted for ASP Classic, hence to data types) Hope they help others too...
这些函数满足了我的要求（适用于 ASP Classic，因此适用于数据类型）希望它们也能帮助其他人......
Function WeekNumber(dDate)
Dim d2
d2 = DateSerial(Year(dDate - WeekDay(dDate - 1) + 4), 1, 3)
WeekNumber = Int((dDate - d2 + WeekDay(d2) + 5) / 7)
End Function
Function YearStart(iWhichYear)
Dim iWeekDay
Dim iNewYear
iNewYear = DateSerial(iWhichYear, 1, 1)
iWeekDay = (iNewYear - 2) Mod 7
If iWeekDay < 4 Then
YearStart = iNewYear - iWeekDay
Else
YearStart = iNewYear - iWeekDay + 7
End If
End Function
Function WeeksInYear(iYear)
WeeksInYear = WeekNumber(DateAdd("d", -1, YearStart(iYear + 1)))
End Function
Function WeekStart(iYear, iWeek)
WeekStart = DateAdd("ww", iWeek - 1, YearStart(iYear))
End Function
Function WeekEnd(iYear, iWeek)
WeekEnd = DateAdd("d", 6, DateAdd("ww", iWeek - 1, YearStart(iYear)))
End Function
回答by Garreth O Mahony
This will give you the start of the current week
这将为您提供本周的开始
dateAdd(DateAdd(DateInterval.Day, (Now.Day * -1), Now)
To get the end of the week add 7 days to the start of the week
要获得一周的结束时间，请在一周的开始时间添加 7 天
回答by ramon posadas
the answer is the following and is the most understandable
答案如下，也是最容易理解的
'1 declaramos las variables
Public firstdayweek As Date 'variable para capturar el valor de inicio de semana de una fecha dada
Public lastdayweek As Date 'variable para el valor de la fecha final de una semana de una fecha dada
Friend Property _NSemana As Integer 'indica el numero de la semana
Friend Property _iniciosemana As Date 'contiene la primer fecha de la semana dada
'Fuciones para codigo
'Funcion para calcular la semana actual en la que estamos
Function semana() As Date
_NSemana = (DateDiff(DateInterval.WeekOfYear, DateTime.Today, New DateTime(DateTime.Today.Year, 1, 1)) *-1)
End Function
'esta funcion es la que llamaremos para setear cada valor puedes colocarlo en cualquier evento
Public Sub damerangosemana()
semana()
_iniciosemana = RangoSemana((_NSemana + 1), Today.Year)
firstdayweek = _iniciosemana
lastdayweek = FinSemana(_iniciosemana)
End Sub
'con esta funcion capturamos el dia de la semana y asignamos la fecha incial
Public Function RangoSemana(ByVal WeekNumber As Integer, ByVal year1 As Integer) As Date
Dim numdia As Integer = 0
Dim oneDate As String
Dim PrimerDia As Date
oneDate = "1/1/" & year1.ToString
PrimerDia = DateAndTime.DateValue(oneDate)
'dayOfYear = inDate.DayOfYear
Select Case PrimerDia.DayOfWeek
Case DayOfWeek.Sunday
numdia = 7
Case DayOfWeek.Monday
numdia = 1
Case DayOfWeek.Tuesday
numdia = 2
Case DayOfWeek.Wednesday
numdia = 3
Case DayOfWeek.Thursday
numdia = 4
Case DayOfWeek.Friday
numdia = 5
Case DayOfWeek.Saturday
numdia = 6
End Select
Dim x As Date = DateAdd(DateInterval.Day, 0 - numdia, CType(oneDate, Date))
Dim startdate As Date = DateAdd(DateInterval.WeekOfYear, WeekNumber - 1, x)
Return startdate
End Function
'funcion para calcular la fecha final
Public Function FinSemana(ByVal Date1 As Date) As Date
Return DateAdd(DateInterval.Day, 7, Date1)
End Function
