MsgBox出现多次

Question

我有一个这样的脚本，一旦用户单击单选按钮，就会出现消息框。但当我点击"否"拨号结果时，消息框会出现两次。我不知道为什么会发生这种事。我不希望它显示两次。我知道一定有一个简单的方法可以解决这个问题我也试着返回函数，但没有成功。

 Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object,      ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
         Dim result As Integer = MessageBox.Show("message", "caption",      MessageBoxButtons.YesNo)
         If result = DialogResult.No Then
             RadioButton1.Checked = False
         ElseIf result = DialogResult.Yes Then
             memoryh4x(&H160ED98, 1, 4)
         End If
     End Sub

Answer 1

您更改RadioButton Checked属性，这将导致第二次调用事件处理程序。

避免这种重新进入事件处理程序的最简单方法是通过全局变量

Dim inCheckedChanged As Boolean = False
......
Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object,      ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
     Try
        ' If we could display the message box..... 
        if inCheckedChanged = False then
           ' Block the reexecution of the MessageBox when clicking NO
            inCheckedChanged = True
            Dim result As Integer = MessageBox.Show("message", "caption",      MessageBoxButtons.YesNo)
            If result = DialogResult.No Then
                ' Now, changing the property reenters the event handler 
                ' but the global variable prevents to get a second messagebox
                RadioButton1.Checked = False
            ElseIf result = DialogResult.Yes Then
                memoryh4x(&H160ED98, 1, 4)
            End If
         End If
    Finally
         InCheckedChanged = False
    End Try
 End Sub

请注意，我将所有内容都放在Try/Finally块中。通过这种方式，如果有东西抛出异常，全局变量InCheckedChanged在从事件处理程序退出之前总是重置为false