Question

我正在尝试使用扩展方法将一周添加到给定日期然后检索一周中第一天的日期（从AddWeeks函数返回的日期）

Private Sub doSomething()
  Dim dt As DateTime = DateTime.Now.AddWeeks(1)

  dt = dt.StartOfWeek(dt.DayOfWeek) ' The year returned here is 0001
End Sub

<Extension()>
    Public Function AddWeeks(ByVal dt As DateTime, numOfWeeks As Integer) As 
    DateTime
        Return dt.AddDays(numOfWeeks * 7)
End Function
<Extension()>



    <Extension()>
Public Function StartOfWeek(ByVal dt As DateTime, start As DayOfWeek) As DateTime
    Dim diff As Integer = dt.DayOfWeek - start
    If (diff < 0) Then
        diff += 7
    End If

    Return dt.AddDays(-diff)
End Function

此代码的问题在于返回的日期是错误的年份，它总是像dd/mm/0001

Answer 1

要到达一周的第一天，请尝试扣除一天，直到您到达星期一为止：

Public Function StartOfWeek(ByVal dt As DateTime, start As DayOfWeek) As DateTime

    If Not dt.DayOfWeek = DayOfWeek.Monday Then

        While dt.DayOfWeek <> DayOfWeek.Monday

            dt = dt.AddDays(-1)

        End While

    End If

    Return dt

End Fuction

vb.net在给定日期添加一周

1 个答案: