尝试捕捉异常不显示消息框和捕捉错误

Question

试图捕捉在计算器中除以零的例外，它不工作，不知道我哪里出错了？

Private Sub btnEqual_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEqual.Click 

    If lblOperator.Text = "+" Then 
     txtAnswer.Text = Val(txtNumberOne.Text) + Val(txtNumberTwo.Text) 
    ElseIf lblOperator.Text = "-" Then 
     txtAnswer.Text = Val(txtNumberOne.Text) - Val(txtNumberTwo.Text) 
    ElseIf lblOperator.Text = "x" Then 
     txtAnswer.Text = Val(txtNumberOne.Text) * Val(txtNumberTwo.Text) 
    ElseIf lblOperator.Text = "/" Then 
     Try 
      txtAnswer.Text = Val(txtNumberOne.Text)/Val(txtNumberTwo.Text) 
     Catch ex As Exception When Val(txtNumberTwo.Text = 0) 
      MessageBox.Show("You cannot divdide by zero") 
     End Try 
    End If 

End Sub 

Answer 1

用零除浮点数返回Infinity，-Infinity或NaN而不是抛出异常。请参阅文档：http://msdn.microsoft.com/en-us/library/25bswc76.aspx