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嘿伙计们，我目前有一个子例程，我希望它会占用日期的日期和月份。然后检查它是哪个月以及该月的天数是否合适

这是我目前拥有的：月份和日期分别是输入的月份和日期

        If Month = 4 Or 6 Or 9 Or 11 Then
            If (1 <= Day) AndAlso (Day <= 30) Then
                DateOkay= True
            End If
        End If


        If Month = 2 Then
            If (1 <= Day) AndAlso (Day <= 28) Then
                DateOkay = True
            End If
        End If


        If Month = 1 Or 3 Or 5 Or 7 Or 8 Or 10 Or 12 Then
            If (1 <= Day) AndAlso (Day <= 31) Then
                DateOkay = True
            End If
        End If

目前，只要天数的输入 <=31，任何月份的 dateOkay 都可以返回。有没有更简单的方法来做到这一点？

提前致谢

4

3 回答 3

4

因为闰年，你也真的需要这一年。有一个内置函数可以提供：

Dim numDays As Integer = DateTime.DaysInMonth(Now.Year, Now.Month)

dateOkay = (day <= numDays)
于 2013-03-30T03:18:50.213 回答
0

这种方法可以让您检查，它消除了将inwhole date拆分为、、的必要性。你可以试试这个whole datedaymonthyear

  Dim xdate As String = "20-02-2013"
  DateOkay = if(IsDate(xdate),true,false) 'This will return true

  xdate = "30-02-2013"
  DateOkay = if(IsDate(xdate),true,false) 'This will return false

编辑：

如果你想向generic validation message用户显示一个 like 'Invalid date.!'，你可以按照这个方法，否则如果你想显示unique messagelike 'Invalid Day.!'，那么你可以DaysInMonth按照 LarsTech 的建议使用。

于 2013-03-30T05:05:52.357 回答
0

我觉得 Larstech 的答案是最好的（假设您DateTime最初使用的是 a ，而不仅仅是月份和日期的整数，或者还有其他获取年份的方法）。

我发布了一个答案来解释为什么你的代码没有按照你期望的方式工作。您的代码给您带来问题的原因是您的条件测试Month不正确并且将始终返回 true，这意味着您的内部 IF 语句将执行。

If Month = 4 Or 6 Or 9 Or 11 Then

6, 9, and 11 will all evaluate to true, making the whole if check true (I believe any non-zero integer value will evaluate to true in VB.NET, but haven't been able to dig up a link to substantiate it. Testing on my machine in VS 2012 supports that, as well as some other discussions I've seen, however).

So what is happening is that the last if block (as you have it written) for the month will always evaluate to True, and as long as the day is 1 to 31 dateOkay will evaluate to true, no matter what the actual month is.

What you should do is this:

If Month = 4 Or Month = 6 Or Month = 9 Or Month = 11 Then

This will evaluate as you expect it to, and the rest or your code will work as expected.

I would recommend using OrElse instead of Or, which will enable you to perform short-circuit evaluation similar to the AndAlso you used. In other words, as soon as one of the conditional tests in the if statement using OrElse evaluates to true, the rest of the conditional tests will be ignored. AndAlso will not evaluate any additional conditional tests once it encounters a False result.

In comparison, And and Or will evaluate all the tests, regardless of outcome. For example, If Month = 1 Or Month = 3 Or Month = 4 Then will run each of the individual tests, even if Month is 1.

Finally, if you're not setting dateOkay before evaluating the date, I would set it explicitly to False before the evaluation. Putting it altogether you'd get something like this:

dateOkay = False

If Month = 4 OrElse Month = 6 OrElse Month = 9 OrElse Month = 11 Then
    If (1 <= Day) AndAlso (Day <= 30) Then
        DateOkay= True
    End If
End If

If Month = 2 Then
    If (1 <= Day) AndAlso (Day <= 28) Then
        DateOkay = True
    End If
End If

If Month = 1 OrElse Month = 3 OrElse Month = 5 OrElse Month = 7 OrElse Month = 8 OrElse Month = 10 OrElse Month = 12 Then
    If (1 <= Day) AndAlso (Day <= 31) Then
        DateOkay = True
    End If
End If

Again, however, Larstech's answer is the best to your question " Is there a simpler way of doing this?".

于 2013-03-30T05:20:46.607 回答