Question

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim UTCTime As Date = TextBox1.Text
        Dim IndianTime As DateTime = UTCTime.AddHours(5.5)
        Dim beforeVal As New TimeSpan(168, 59, 59)
        Dim beforeVal1 As New TimeSpan(72, 59, 59)
        Dim beforeVal2 As New TimeSpan(23, 59, 59)
        Label1.Text = IndianTime.AddSeconds(-beforeVal.TotalSeconds).ToString("G")
        Label2.Text = IndianTime.AddSeconds(-beforeVal1.TotalSeconds).ToString("G")
        Label3.Text = UTCTime.AddSeconds(-beforeVal2.TotalSeconds).ToString("G")

        '////////////

        Dim UTCTime1 As Date = Date.UtcNow
        Dim IndianTime1 As DateTime = UTCTime1.AddHours(5.5)
        Label4.Text = IndianTime1.ToString("G")
        If CType(Label4.Text, Date) >= CType(Label3.Text, Date) Then
            Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
        ElseIf CType(Label4.Text, Date) >= CType(Label2.Text, Date) Then
            Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
        ElseIf CType(Label4.Text, Date) >= CType(Label1.Text, Date) Then
            Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
        Else
            Label5.Text = "Print"
        End If



    End Sub

错误：

它将始终在label5中显示msg 对不起！门票不能在当天或旅行日期后取消如果我只使用单端if语句那么它工作正常。 ...如果我使用上面提到的3个条件，它将在label5中显示错误消息为抱歉！机票不能在当天或旅行日期后取消

如果我使用它而不是上面的代码....那么它工作正常

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim UTCTime1 As Date = Date.UtcNow
        Dim IndianTime1 As DateTime = UTCTime1.AddHours(5.5)
        Label4.Text = IndianTime1.ToString("G")
        If CType(Label4.Text, Date) >= CType(Label3.Text, Date) Then
            Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
        Else
            Label5.Text = "Print"
        End If
    End Sub
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim UTCTime As Date = TextBox1.Text
        Dim IndianTime As DateTime = UTCTime.AddHours(5.5)
        Dim beforeVal As New TimeSpan(168, 59, 59)
        Dim beforeVal1 As New TimeSpan(72, 59, 59)
        Dim beforeVal2 As New TimeSpan(23, 59, 59)
        Label1.Text = IndianTime.AddSeconds(-beforeVal.TotalSeconds).ToString("G")
        Label2.Text = IndianTime.AddSeconds(-beforeVal1.TotalSeconds).ToString("G")
        Label3.Text = UTCTime.AddSeconds(-beforeVal2.TotalSeconds).ToString("G")
    End Sub

Answer 1

在没有运行代码的情况下，我能看到的最明显的事情是：

Dim UTCTime As Date = TextBox1.Text

您正在尝试将字符串分配给Date变量。使用DateTime.TryParse或DateTime.TryParseExact将字符串安全地转换为日期。

<强>更新
我现在更仔细地查看了您的代码，并找到了以下内容：

您正在创建DateTime值，转换为您转换回DateTime值的字符串以进行比较。为什么不首先使用DateTime值？每次转换都是可能的失败点。
您正在三个不同的时间间隔进行比较，但每个都会导致相同的错误消息。这意味着如果与最小日期的比较失败，则无需测试其他日期，因为它会导致相同的结果。

所以我建议你这样编写你的方法：

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim UTCTime As Date
    If DateTime.TryParse(TextBox1.Text, UTCTime) Then
        Dim IndianTime As DateTime = UTCTime.AddHours(5.5)
        Dim comparisonDateTime As DateTime = IndianTime.Add(New TimeSpan(23, 59, 59))

        ''#////////////

        Dim utcNow As Date = Date.UtcNow
        Dim IndianTime1 As DateTime = utcNow.AddHours(5.5)
        If IndianTime1 >= comparisonDateTime Then
            Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
        Else
            Label5.Text = "Print"
        End If
    Else
        ''# TextBox1 did not contain a valid date, inform the user in some way
    End If
End Sub

Answer 2

为什么要使用Label.Text属性进行比较？

标签没有有意义的名称，它们是从您已有的DateTime变量中转换而来的。

您有三个由ElseIf链接的条件，这些条件都会导致相同的操作，这应该是一个If OrElse s。

正如Fredrik指出的那样，初始隐式分配将无法通过严格的转换。

简化：

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim UTCTime As Date = DateTime.Parse(TextBox1.Text)
    Dim IndianTime As DateTime = UTCTime.AddHours(5.5)
    Dim IndianTime1 As DateTime = Date.UtcNow.AddHours(5.5)

    Dim beforeValOffset As New TimeSpan(168, 59, 59)
    Dim beforeVal1Offset As New TimeSpan(72, 59, 59)
    Dim beforeVal2OffSet As New TimeSpan(23, 59, 59)

    Dim beforeVal As DateTime = IndianTime.Subtract(beforeValOffset)
    Dim beforeVal1 As DateTime = IndianTime.Subtract(beforeVal1Offset)
    Dim beforeVal2 As DateTime = UTCTime.Subtract(beforeVal2OffSet)

    Label1.Text = beforeVal.ToString("G")
    Label2.Text = beforeVal1.ToString("G")
    Label3.Text = beforeVal2.ToString("G")
    Label4.Text = IndianTime1.ToString("G")

    If (IndianTime1 >= beforeVal2) OrElse _
            (IndianTime1 >= beforeVal1) OrElse _
            (IndianTime1 >= beforeVal) Then
        Label5.Text = "Sorry ! Ticket cannot be cancelled on same day or after journey date"
    Else
        Label5.Text = "Print"
    Endif
End Sub

我稍微改变了你的功能。我仍然不知道你真正希望实现什么，但我希望重写可以帮助你了解你实际在做什么。

这个vb.net代码有什么问题吗？

2 个答案: