对于日期值的下一个循环

Question

如何修复以下代码？

Dim xx As Date = New DateTime(2016, 1, 1)
Dim yy As Date = New DateTime(2016, 12, 31)
For ii = xx To yy
    MsgBox(ii)
Next ii

这是错误：

Answer 1

如错误消息所示，您不能通过向其添加1来增加日期。假设你打算做的是添加一天，你可以使用AddDays方法。

    Dim xx As Date = New DateTime(2016, 12, 29)
    Dim yy As Date = New DateTime(2016, 12, 31)
    Dim ii As Date = xx
    Do Until ii > yy
        MessageBox.Show(ii.ToShortDateString)
        ii = ii.AddDays(1)
    Loop

Answer 2

您可以使用While循环：

While xx <= yy  
    MsgBox(xx)
    xx = xx.AddDays(1)  
End While

或Enumerable.Range：

Dim days = Enumerable.Range(0, Convert.ToInt32((yy-xx).TotalDays))
    .Select(Function(i) xx.AddDays(i))
For Each DateTime day in days
   MsgBox(day)
Next day

（看起来很复杂，但是开始考虑描述数据而不是构建循环是很好的。）

或For循环：

Dim count = Convert.ToInt32((yy-xx).TotalDays)
For i As Integer To Count
    MsgBox(xx.AddDays(i))
Next i

Answer 3

Dim xx As Date = New DateTime(2016, 1, 1)
Dim yy As Date = New DateTime(2016, 12, 31)

Dim intNumDays As Integer = CInt(Math.Ceiling((yy - xx).TotalDays))
For ii As Integer = 0 To intNumDays - 1
  MsgBox(xx.AddDays(ii))
Next ii