Question

我有一个学校的VB项目。当用户尝试关闭表单时，我必须创建一个YesNo样式的消息框。如果用户按“是”，则应用程序关闭;如果用户按“否”，则返回程序屏幕。问题是，当我按“否”时，应用程序仍然关闭，我不知道VB是否有故障，但它显示两个消息框。我是VB的新手（上个月开始）。这是代码：

Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
    Dim closing As MsgBoxResult
    closing = MsgBox("Are you sure you want to exit?", MsgBoxStyle.YesNo Or MsgBoxStyle.Question,)
    If closing = MsgBoxResult.Yes Then Application.Exit()
End Sub

Answer 1

关闭已经开始时发生FormClosing事件。

您需要取消结束，而不是致电Application.Exit。 Application.Exit的调用再次触发结束事件。因此，MessageBox出现两次。

如果e.Cancel = True的结果为MessageBox，请设置No：

Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
    If MsgBox("Are you sure you want to exit?", MsgBoxStyle.YesNo Or MsgBoxStyle.Question) = MsgBoxResult.No Then
        e.Cancel = True
    End If
End Sub

Answer 2

由于您处于Form.Closing事件中，除非您致电e.Cancel = True，否则表单将会关闭。

Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
    Dim closing As MsgBoxResult
    closing = MsgBox("Are you sure you want to exit?", MsgBoxStyle.YesNo Or MsgBoxStyle.Question,)
    If closing = MsgBoxResult.No Then 
         e.Cancel = True
    End If
End Sub

尝试编写FormClosing时出现问题

2 个答案: