Question

我当前的作业让我使用try and catch块进行错误处理。该代码应该计算超过500的值以输入特定值，并且在500以下计算不同的值。我的问题是我不知道把尝试和捕获处理线放在哪里。如果我在dueLbl.Text = "your payment is " & FormatCurrency(totalDue)之后将try放在if语句和catch语句之上我收到了endif must match if,else must precede if，并且从未接触过。现在，如果我将try放在if语句之上并将catch留在最底部，代码将会运行但仍然不会捕获任何内容。

Public Class Form1


    Private Sub calcButton_Click(sender As Object, e As EventArgs) Handles calcButton.Click

        Dim kwHour As Double
        Dim totalDue As Double
        Dim basePay As Double
        Dim overBasePay As Double


        kwHour = kwhourValue.Text

        If kwHour <= 500 Then
            totalDue = kwHour * 0.27
            dueLbl.Text = "your payment is " & FormatCurrency(totalDue)

        Else
            basePay = 500 * 0.27
            overBasePay = (kwHour - 500) * 0.55

            totalDue = basePay + overBasePay
            dueLbl.Text = "your payment is " & FormatCurrency(totalDue)
        End If

    End Sub
End Class

Answer 1

你可以这样做......

Private Sub calcButton_Click(sender As Object, e As EventArgs) Handles calcButton.Click
    Try
    Dim kwHour As Double
    Dim totalDue As Double
    Dim basePay As Double
    Dim overBasePay As Double


    kwHour = kwhourValue.Text

    If kwHour <= 500 Then
        totalDue = kwHour * 0.27
        dueLbl.Text = "your payment is " & FormatCurrency(totalDue)

    Else
        basePay = 500 * 0.27
        overBasePay = (kwHour - 500) * 0.55

        totalDue = basePay + overBasePay
        dueLbl.Text = "your payment is " & FormatCurrency(totalDue)
    End If
    Catch ex as Exception
        MsgBox(ex.message)
    Finally
    'Whatever you want to do...
    End Try
End Sub

您不能将Try Catch语句放在IF语句的中间。这不会正确结束您的IF声明。上面的代码将捕获它在执行代码时遇到的任何错误。此外，您还可以添加Finally。无论下面的代码是什么代码都会在遇到错误后执行。有点像结局代码：）

Answer 2

当你说

时

现在，如果我将try保留在if语句之上并将catch保留在最底层，代码将会运行但仍然无法捕获任何内容。

我猜你在

中收到了错误

kwHour = kwhourValue.Text

所以你可以做的是将try语句放在try行块中包含该行的那一行之前。我在这里假设你被要求专门使用try catch块。否则，还有其他方法可以在这里做。你的任务到底是什么意思？

Answer 3

通过这种方式......顺便说一句，您需要将kwhourValue.Text转换为Double

Private Sub calcButton_Click(sender As Object, e As EventArgs) Handles calcButton.Click

    Dim kwHour As Double
    Dim totalDue As Double
    Dim basePay As Double
    Dim overBasePay As Double

  Try

    If Double.TryParse(kwhourValue.Text, kwHour) Then
       ' text is convertible to Double, and kwHour contains the Double value now
    Else
       ' Cannot convert text to Double
        End Sub
    End If

    If kwHour <= 500 Then
        totalDue = kwHour * 0.27
        dueLbl.Text = "your payment is " & FormatCurrency(totalDue)
    Else
        basePay = 500 * 0.27
        overBasePay = (kwHour - 500) * 0.55
        totalDue = basePay + overBasePay
        dueLbl.Text = "your payment is " & FormatCurrency(totalDue)
    End If

  Catch ex as Exception
    MsgBox(ex.message)
  Finally
    'Whatever you want to do...
  End Try
End Sub

错误处理：如果......那么就不能放置Try ... catch

3 个答案: