Question

我使用以下代码确定下一周每一天的日期：

    Dim someDate As DateTime = Date.Today 

    Dim nextMonday As DateTime = someDate
    While nextMonday.DayOfWeek <> DayOfWeek.Monday
        nextMonday = nextMonday.AddDays(1)
    End While

    Dim nextTuesday As DateTime = someDate
    While nextTuesday.DayOfWeek <> DayOfWeek.Tuesday
        nextTuesday = nextTuesday.AddDays(1)
    End While

除了与当天相同的未来日外，它的效果很好。例如。今天是2016年8月8日星期五，代码也返回2016年8月1日，它实际上应该返回15/1/2016。其他日子的所有日期都是正确的。有什么想法吗？

此致

Answer 1

您可以使用以下扩展方法：

<System.Runtime.CompilerServices.Extension()> _
Public Function StartOfWeek(dt As DateTime, firstDayOfWeek As DayOfWeek) As DateTime
    Dim diff As Int32 = dt.DayOfWeek - firstDayOfWeek
    If diff < 0 Then
        diff += 7
    End If

    Return dt.AddDays(-1 * diff).Date
End Function

如果您希望下周完成List(Of Date)：

Dim startOfNextWeek As Date = Date.Today.AddDays(7).StartOfWeek(DayOfWeek.Monday)
Dim nextWeek = Enumerable.Range(0, 7).Select(Function(d) startOfNextWeek.AddDays(d)).ToList()

没有LINQ：

Dim nextWeek As New List(Of Date)
For d As Int32 = 0 To 6
    nextWeek.Add(startOfNextWeek.AddDays(d))
Next

Answer 2

使用循环遍历值的函数会更好。这样的事情应该做你想做的事情：

Public Function FindNextDayOfWeek(startDate As Date, dayToFind As DayOfWeek) As Date
    Dim adjustment = 6 + (dayToFind - startDate.DayOfWeek)
    If adjustment > 7 Then adjustment -= 7
    Return startDate.AddDays(adjustment)
End Function

试验：

FindNextDayOfWeek(#2015-01-13#, DayOfWeek.Tuesday) 'returns 19/01/2015
FindNextDayOfWeek(#2015-01-11#, DayOfWeek.Wednesday) ' returns 13/01/2015
FindNextDayOfWeek(#2015-01-11#, DayOfWeek.Monday) 'returns 18/01/2015

Answer 3

此方法适用于您：

Private Function GetNextDayOfWeek(afterDate As Date, targetDayOfWeek As DayOfWeek) As DateTime
    Const TotalDaysInWeek = DayOfWeek.Saturday - DayOfWeek.Sunday + 1 '+1 to account for zero indexed.
    Dim daysToAdd As Integer

    Select Case targetDayOfWeek
        Case Is < afterDate.DayOfWeek
            daysToAdd = afterDate.DayOfWeek - targetDayOfWeek - 1
        Case Is = afterDate.DayOfWeek
            daysToAdd = TotalDaysInWeek 'need to find exactly one week from "afterDate"
        Case Is > afterDate.DayOfWeek
            daysToAdd = targetDayOfWeek - afterDate.DayOfWeek
    End Select

    Return afterDate.AddDays(daysToAdd)
End Function

VB.NET获取下周的日期

3 个答案: