vb.net - 如何处理 VB.NET 程序中因无效用户输入而导致的错误？

Question

我是 VB.NET 的初学者，我想知道如何处理程序用户可能出现的错误。例如，我有一个三角形区域程序，我要求程序用户在文本框中插入三角形的底长和高度。但是如果他插入一个字母或其他东西，比如一个标志怎么办……我的程序就会崩溃……

我知道一种方法是使用On Error GoTo，但我不知道如何操作。如果您可以引导我访问某些链接，或者您可以解释我如何处理错误，我将不胜感激。也许您甚至可以向我展示其他方法来避免用户输入错误。

这是我到目前为止的小程序:

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
                Handles Button1.Click

    Dim , Height, ARIA As Integer

    Base = TextBox1.Text
    Height = TextBox2.Text
    ARIA =  Base * Height / 2
    TextBox3.Text = ARIA

End Sub

Answer 1

您需要做的是:

Try
    'Do something dangerous
Catch ex As System.Exception 'catch any error
    'Handle the error here
End Try

如果您有任何需要执行的“清理”任务，无论是否发生任何错误(例如关闭文件)，请执行以下操作:

Try
    'The dangerous code here will get executed
Finally
    'Whether the code throws any exception or not, this part will ALWAYS run
End Try
'If there was any error, then it would be thrown AFTER the end of the 'finally'

您还可以拥有更复杂的异常处理程序，例如:

Try
    'Dangerous code
Catch ex As FormatException
    'This code catches only a FormatException
Catch ex As ArithmeticException
    'This code catches only ArithmeticException
'Any other kind of error is NOT caught
Finally
    'Regardless of whether the error was handled, this part will execute
End Try
'Unhandled exceptions will be thrown before the block continues