我正在尝试在我的父表单上实现一个功能，当事件触发时，我想对所有打开的子表单执行操作。因为任何给定的子表单在给定时间可能会或可能不会打开，所以我无法直接从父表单上的事件处理它：即，不能执行以下操作，因为当时可能不会启动 Child1：
--Parent Form--
Public Sub ParentEvent()
DoParentAction()
DoChild1Action()
DoChild2Action()
End Sub
每个子页面上是否有办法监听 ParentEvent() 被触发？本质上，我想做的是在子页面上处理被触发的 ParentEvent()，就像在子页面上单击按钮一样，如下所示：
--Child1--
Public Sub ChildEvent() Handles ParentForm.DoParentAction()
DoChild1Action()
End Sub
这很容易做到，您只需要绕过 VBWithEvents和Handles语法即可。
Public Class ParentForm
Event OnDoSomething()
Private Sub DoSomething()
RaiseEvent OnDoSomething()
End Sub
End Class
进而
Public Class ChildForm
Public Sub New()
InitializeComponent()
AddHandler ParentForm.OnDoSomething, AddressOf DoSomething
End Sub
Private Sub DoSomething()
' do something
End Sub
Private Sub ChildForm_FormClosing(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.FormClosingEventArgs) _
Handles MyBase.FormClosing
RemoveHandler ParentForm.OnDoSomething, AddressOf DoSomething
End Sub
End Class
务必确保在处置子表单之前删除事件处理程序（否则最终会导致内存泄漏），这一点很重要。
以上假设您使用的是 VB 默认实例ParentForm- 如果不是，显然您必须相应地引用事物。更好的方法可能是让父级在构造函数中成为参数，例如：
Public Sub New(ByVal parent as ParentForm)
InitializeComponent()
AddHandler parent.OnDoSomething, AddressOf DoSomething
End Sub
当然，还要修改该RemoveHandler部分（您需要保留对父级的引用）。ParentChanged如果这是一个 MDI 应用程序，另一种选择是在事件中挂钩/取消挂钩。
唯一需要注意的是，您不能在父窗体的构造函数中创建任何子窗体，因为在构造过程中最终会出现自引用。
当然。
向父窗体添加公共事件：
Public Event EventFired(ByVal timestamp As DateTime)
在每个子窗体中，添加一个处理程序：
Public Sub ParentEventFired(ByVal timestamp As DateTime)
Label1.Text = "Child 1: Parent Event Fired (" & timestamp.ToLongTimeString() & ")"
End Sub
创建子表单时，添加一个处理程序：
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim l_child1 = New ChildForm1()
AddHandler Me.EventFired, AddressOf l_child1.ParentEventFired
l_child1.Show(Me)
End Sub
无论您使用的是 MDI 还是简单的自由浮动窗口，您都可以使用这种方法。
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class ParentForm
Inherits System.Windows.Forms.Form
'Form overrides dispose to clean up the component list.
<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing AndAlso components IsNot Nothing Then
components.Dispose()
End If
Finally
MyBase.Dispose(disposing)
End Try
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
Me.Button1 = New System.Windows.Forms.Button
Me.Button2 = New System.Windows.Forms.Button
Me.Button3 = New System.Windows.Forms.Button
Me.SuspendLayout()
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(12, 12)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(166, 23)
Me.Button1.TabIndex = 0
Me.Button1.Text = "Open Child 1"
Me.Button1.UseVisualStyleBackColor = True
'
'Button2
'
Me.Button2.Location = New System.Drawing.Point(12, 41)
Me.Button2.Name = "Button2"
Me.Button2.Size = New System.Drawing.Size(166, 23)
Me.Button2.TabIndex = 0
Me.Button2.Text = "Open Child 2"
Me.Button2.UseVisualStyleBackColor = True
'
'Button3
'
Me.Button3.Location = New System.Drawing.Point(12, 231)
Me.Button3.Name = "Button3"
Me.Button3.Size = New System.Drawing.Size(166, 23)
Me.Button3.TabIndex = 0
Me.Button3.Text = "Fire Event"
Me.Button3.UseVisualStyleBackColor = True
'
'ParentForm
'
Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Controls.Add(Me.Button3)
Me.Controls.Add(Me.Button2)
Me.Controls.Add(Me.Button1)
Me.Name = "ParentForm"
Me.Text = "ParentForm"
Me.ResumeLayout(False)
End Sub
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents Button2 As System.Windows.Forms.Button
Friend WithEvents Button3 As System.Windows.Forms.Button
End Class
Public Class ParentForm
Public Event EventFired(ByVal timestamp As DateTime)
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim l_child1 = New ChildForm1()
AddHandler Me.EventFired, AddressOf l_child1.ParentEventFired
l_child1.Show(Me)
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim l_child2 = New ChildForm2()
AddHandler Me.EventFired, AddressOf l_child2.ParentEventFired
l_child2.Show(Me)
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
RaiseEvent EventFired(DateTime.Now)
End Sub
End Class
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class ChildForm1
Inherits System.Windows.Forms.Form
'Form overrides dispose to clean up the component list.
<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing AndAlso components IsNot Nothing Then
components.Dispose()
End If
Finally
MyBase.Dispose(disposing)
End Try
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
Me.Label1 = New System.Windows.Forms.Label
Me.SuspendLayout()
'
'Label1
'
Me.Label1.AutoSize = True
Me.Label1.Location = New System.Drawing.Point(12, 9)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(39, 13)
Me.Label1.TabIndex = 0
Me.Label1.Text = "Label1"
'
'ChildForm1
'
Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Controls.Add(Me.Label1)
Me.Name = "ChildForm1"
Me.Text = "ChildForm1"
Me.ResumeLayout(False)
Me.PerformLayout()
End Sub
Friend WithEvents Label1 As System.Windows.Forms.Label
End Class
Public Class ChildForm1
Public Sub ParentEventFired(ByVal timestamp As DateTime)
Label1.Text = "Child 1: Parent Event Fired (" & timestamp.ToLongTimeString() & ")"
End Sub
End Class
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class ChildForm2
Inherits System.Windows.Forms.Form
'Form overrides dispose to clean up the component list.
<System.Diagnostics.DebuggerNonUserCode()> _
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
Try
If disposing AndAlso components IsNot Nothing Then
components.Dispose()
End If
Finally
MyBase.Dispose(disposing)
End Try
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnostics.DebuggerStepThrough()> _
Private Sub InitializeComponent()
Me.Label1 = New System.Windows.Forms.Label
Me.SuspendLayout()
'
'Label1
'
Me.Label1.AutoSize = True
Me.Label1.Location = New System.Drawing.Point(12, 9)
Me.Label1.Name = "Label1"
Me.Label1.Size = New System.Drawing.Size(39, 13)
Me.Label1.TabIndex = 1
Me.Label1.Text = "Label1"
'
'ChildForm2
'
Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font
Me.ClientSize = New System.Drawing.Size(292, 266)
Me.Controls.Add(Me.Label1)
Me.Name = "ChildForm2"
Me.Text = "ChildForm2"
Me.ResumeLayout(False)
Me.PerformLayout()
End Sub
Friend WithEvents Label1 As System.Windows.Forms.Label
End Class
Public Class ChildForm2
Public Sub ParentEventFired(ByVal timestamp As DateTime)
Label1.Text = "Child 2: Parent Event Fired (" & timestamp.ToLongTimeString() & ")"
End Sub
End Class