VB.NET 4.7.2多窗体应用：如何跨窗体处理Form开闭事件？

核心思路：集中式事件管理替代逐个窗体触发 #

不需要每个窗体单独处理本地事件再转发全局事件，直接用以下两种简洁方案实现：

方式一：全局事件管理器类 #

写一个静态类统一托管所有窗体的打开/关闭事件，所有窗体只需注册一次，其他窗体直接监听全局事件即可：

Public Class FormEventManager
    ' 定义全局事件
    Public Shared Event FormOpened(sender As Form)
    Public Shared Event FormClosed(sender As Form)

    ' 窗体注册方法
    Public Shared Sub RegisterForm(form As Form)
        AddHandler form.Load, AddressOf OnFormLoaded
        AddHandler form.FormClosed, AddressOf OnFormClosed
    End Sub

    Private Shared Sub OnFormLoaded(sender As Object, e As EventArgs)
        RaiseEvent FormOpened(CType(sender, Form))
    End Sub

    Private Shared Sub OnFormClosed(sender As Object, e As FormClosedEventArgs)
        RaiseEvent FormClosed(CType(sender, Form))
    End Sub
End Class

使用步骤：

1. 每个窗体的Load事件中添加一行注册代码：

FormEventManager.RegisterForm(Me)

2. 在需要更新菜单的窗体（比如主窗体）中订阅全局事件：

AddHandler FormEventManager.FormOpened, AddressOf UpdateWindowMenu
AddHandler FormEventManager.FormClosed, AddressOf UpdateWindowMenu

Private Sub UpdateWindowMenu(sender As Form)
    ' 这里实现「窗口」菜单的更新逻辑，比如添加/移除菜单项
End Sub

方式二：直接利用Application.OpenForms集合 #

借助Application.OpenForms实时获取已打开窗体，结合Application.NewForm事件捕获新窗体创建：

' 主窗体Load事件初始化
Private Sub MainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ' 注册已打开的窗体事件
    For Each frm As Form In Application.OpenForms
        RegisterFormEvents(frm)
    Next
    ' 监听新窗体创建事件
    AddHandler Application.NewForm, AddressOf OnNewFormCreated
End Sub

Private Sub OnNewFormCreated(sender As Object, e As FormEventArgs)
    RegisterFormEvents(e.Form)
    UpdateWindowMenu()
End Sub

Private Sub RegisterFormEvents(form As Form)
    AddHandler form.FormClosed, AddressOf OnFormClosed
End Sub

Private Sub OnFormClosed(sender As Object, e As FormClosedEventArgs)
    UpdateWindowMenu()
End Sub

Private Sub UpdateWindowMenu()
    ' 刷新菜单：清空后重新遍历已打开窗体添加菜单项
    WindowMenu.DropDownItems.Clear()
    For Each frm As Form In Application.OpenForms
        If frm IsNot Me Then ' 可选：排除主窗体
            Dim menuItem As New ToolStripMenuItem(frm.Text)
            AddHandler menuItem.Click, Sub() frm.BringToFront()
            WindowMenu.DropDownItems.Add(menuItem)
        End If
    Next
End Sub

注意事项 #

• Application.NewForm事件可覆盖FormOpening场景，在窗体创建时立即触发；
• 若需监听FormClosing事件，只需在RegisterFormEvents中添加对应事件处理器；
• 注意内存泄漏：若窗体生命周期独立于主窗体，记得在窗体关闭时移除事件处理器。

内容的提问来源于stack exchange，提问作者Scott