覆盖 VB.NET 中的事件

Question

我想隐藏/覆盖 VB.NET 中的事件。

我这样做只是因为我必须在此对象中实现一个接口，该接口包含与基础对象本身相同的事件，并且我需要保持此基础事件不变，无需修改，也无需添加补充事件。

我该怎么做呢？

Public Shadows Event VisibleChanged As EventHandler Implements IVisibleChanged

因此，我想实现一个包含 VisibleChanged 事件的接口，但也要保持 myBase VisibleChanged 事件的功能。

  Public Shadows Event VisibleChanged As EventHandler Implements IVisibleChanged
    AddHandler(ByVal value As EventHandler)
      AddHandler MyBase.VisibleChanged, value
    End AddHandler
    RemoveHandler(ByVal value As EventHandler)
      RemoveHandler MyBase.VisibleChanged, value
    End RemoveHandler
  End Event

像这样的东西，但 Visual Studio 似乎无法识别这样的语法...

我的意思是，在 C# 中我是这样实现的：

public new event EventHandler VisibleChanged
{
    add { base.VisibleChanged += value; }
    remove { base.VisibleChanged -= value; }
}

Answer 1

您可以重写派生类中的处理程序吗？

Public Class OverriddenClass
Inherits OriginalClass
Protected Overrides Function ProcessVisibleChanged(ByRef msg as Message, value as ...) As Boolean
  value = value + 1
  ProcessVisibleChanged = MyBase.ProcessVisibleChanged(msg, value)
  ' or use OnVisibleChanged to avoid the base handler
End Function
end class

Answer 2

  Public Shadows Event VisibleChanged As EventHandler Implements IVisibleChanged
    AddHandler(ByVal value As EventHandler)
      AddHandler MyBase.VisibleChanged, value
    End AddHandler
    RemoveHandler(ByVal value As EventHandler)
      RemoveHandler MyBase.VisibleChanged, value
    End RemoveHandler
  End Event

像这样的东西，但 Visual Studio 似乎无法识别这样的语法...

我的意思是，在 C# 中我是这样实现的：

public new event EventHandler VisibleChanged
{
    add { base.Click += value; }
    remove { base.Click -= value; }
}

Answer 3

Option Strict On
Option Explicit On

Public Class Form1
  Public Sub New()
    ' This call is required by the Windows Form Designer.'
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.'
    Dim b As New MyButton
    Me.Controls.Add(b)
    b.Name = "customButton"
    b.Location = New Point(10, 10)
    b.Text = "Hit me!"
    AddHandler CType(b, IMyInterface).Click, AddressOf MyButton1_Click
  End Sub

  Private Sub MyButton1_Click( _ 
      ByVal sender As System.Object, ByVal e As System.EventArgs)
    Debug.Print("{0} clicked!; ", CType(sender, Control).Name)
  End Sub
End Class

' ------- interface'
Public Interface IMyInterface
  Event Click As EventHandler
End Interface

' ------- class'
Public Class MyButton
  Inherits System.Windows.Forms.Button
  Implements IMyInterface
  ' ============ HERE IS THE SOLUTION'
  Private Event Click1 As EventHandler Implements IMyInterface.Click

  Private Sub ResendClick( _ 
      ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Click
    RaiseEvent Click1(sender, e)
  End Sub
  ' END HERE IS THE SOLUTION ============ '
End Class

Answer 4

在 VB.NET 中实现接口时，不需要将实现命名为与接口相同的名称。

接口示例：

Public Interface IFoo
    Event Bar As EventHandler
End Interface

实现示例：

Public Class FooImplementation
    Implements IFoo

    ' This is the built-in Bar event, specific to this class.
    Public Event Bar As EventHandler

    ' This is the implemented IFoo.Bar event.
    Public Event IFooBar As EventHandler Implements IFoo.Bar

End Class

当某人作为 IFoo 附加到您时，他们将获得您的 IFooBar 事件：

Dim instance As IFoo = New FooImplementation()
AddHandler instance.Bar, AddressOf IFooBarHandler

当他们作为 FooImplementation 附加到您时，他们将获得 Bar 事件，并且他们还能够附加到 IFooBar :

Dim instance As New FooImplementation()
AddHandler instance.Bar, AddressOf BarHandler
AddHandler instance.IFooBar, AddressOf IFooBarHandler