如何使用 vb.net 根据周数获取一周的开始日期？
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How to get starting date in a Week based on week number using vb.net?
提问by J-J
I need help on getting the starting date of a week from a given week number in vb.net.
我需要帮助从 vb.net 中的给定周数获取一周的开始日期。
I have combobox binded with items 1-53 as week numbers. What I want to do is whenever I select a specific week number, it will return the first date of that selected week number.
我将组合框与项目 1-53 绑定为周数。我想要做的是每当我选择特定的周数时，它都会返回所选周数的第一个日期。
For instance I have selected week Number 46, it must return November 11, 2013 as first date of week number 46.
例如，我选择了第 46 周，它必须返回 2013 年 11 月 11 日作为第 46 周的第一个日期。
I have tried the following codes and it returns only the first date of a week from a current week number.
我尝试了以下代码，它仅从当前周数返回一周的第一个日期。
DateAdd("d", -Weekday(Now, FirstDayOfWeek.Monday) + 1, Now)
Is there any possible way that can return my expected output?
有什么可能的方法可以返回我的预期输出吗？
Please help me. Thanks in advance.
请帮我。提前致谢。
采纳答案by vbigham
You could try something like this:
你可以尝试这样的事情：
Private Sub TestDateAdd()
Dim weekStart As DateTime = GetWeekStartDate(46, 2013)
Console.WriteLine(weekStart)
End Sub
Private Function GetWeekStartDate(weekNumber As Integer, year As Integer) As Date
Dim startDate As New DateTime(year, 1, 1)
Dim weekDate As DateTime = DateAdd(DateInterval.WeekOfYear, weekNumber - 1, startDate)
Return DateAdd(DateInterval.Day, (-weekDate.DayOfWeek) + 1, weekDate)
End Function
Disclaimer: I only really tested this with the one input, you probably want to make sure that it works as expected for different years, etc..
免责声明：我只真正用一个输入测试过这个，你可能想确保它在不同的年份都能按预期工作，等等。
回答by Jike
Public Function FirstDateOfWeek(ByVal Year As Integer, ByVal Week As Integer, Optional FirstDayOfWeek As DayOfWeek = DayOfWeek.Monday) As Date
Dim dt As Date = New Date(Year, 1, 1)
If dt.DayOfWeek > 4 Then dt = dt.AddDays(7 - dt.DayOfWeek) Else dt = dt.AddDays(-dt.DayOfWeek)
dt = dt.AddDays(FirstDayOfWeek)
Return dt.AddDays(7 * (Week - 1))
End Function
