继承适用于第一个后代但不适用于下一个。为什么？

Question

Form1中

Public Class Form1

Private Sub But_Bell_Click(sender As System.Object, e As System.EventArgs) Handles But_Bell.Click
    MessageBox.Show("Ding a ling")
End Sub

结束班

第一个后裔

Public Class BellsAndWhistles
Inherits Form1
Friend WithEvents But_Whistle As System.Windows.Forms.Button

Private Sub InitializeComponent()
    Me.But_Whistle = New System.Windows.Forms.Button()
    Me.SuspendLayout()
    '
    'But_Whistle
    '
    Me.But_Whistle.Location = New System.Drawing.Point(112, 38)
    Me.But_Whistle.Name = "But_Whistle"
    Me.But_Whistle.Size = New System.Drawing.Size(75, 23)
    Me.But_Whistle.TabIndex = 1
    Me.But_Whistle.Text = "Whistle"
    Me.But_Whistle.UseVisualStyleBackColor = True
    '
    'BellsAndWhistles
    '
    Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
    Me.ClientSize = New System.Drawing.Size(292, 273)
    Me.Controls.Add(Me.But_Whistle)
    Me.Name = "BellsAndWhistles"
    Me.Text = "Bells & Whistles"
    Me.Controls.SetChildIndex(Me.But_Whistle, 0)
    Me.ResumeLayout(False)

End Sub

Private Sub But_Whistle_Click(sender As System.Object, e As System.EventArgs) Handles But_Whistle.Click
    MessageBox.Show("Toot Toot")
End Sub

结束班

第二个后裔

Public Class MoreBellsAndWhistles
Inherits BellsAndWhistles
Friend WithEvents MoreBells As System.Windows.Forms.Button

Private Sub InitializeComponent()
    Me.MoreBells = New System.Windows.Forms.Button()
    Me.SuspendLayout()
    '
    'MoreBells
    '
    Me.MoreBells.Location = New System.Drawing.Point(30, 145)
    Me.MoreBells.Name = "MoreBells"
    Me.MoreBells.Size = New System.Drawing.Size(75, 23)
    Me.MoreBells.TabIndex = 1
    Me.MoreBells.Text = "More Bells"
    Me.MoreBells.UseVisualStyleBackColor = True
    '
    'MoreBellsAndWhistles
    '
    Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!)
    Me.ClientSize = New System.Drawing.Size(292, 273)
    Me.Controls.Add(Me.MoreBells)
    Me.Name = "MoreBellsAndWhistles"
    Me.Text = "MoreBellsAndWhistles"
    Me.Controls.SetChildIndex(Me.MoreBells, 0)
    Me.ResumeLayout(False)

End Sub

Private Sub MoreBells_Click(sender As System.Object, e As System.EventArgs) Handles MoreBells.Click
    MessageBox.Show("Ting TIng")
End Sub

Private Sub MoreBellsAndWhistles_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

End Sub

结束班

哨子按钮哪里消失了？

继承的类部分有效，因为您可以通过代码访问它。

Answer 1

尝试从第二个后代调用MyBase.InitializeComponent()。您可能还必须更改它的访问级别。

修改

这整夜困扰着我。事实证明，这是一个缺少构造函数的情况。如果您使用反射器，您会看到Form1有一个调用Me.InitializeComponent()的构造函数，即使Form1.vb或Form1.Designer.vb中不存在。

<DesignerGenerated> _
Public Class Form1
    Inherits Form
    ' Methods
    Public Sub New()
        Me.InitializeComponent
    End Sub

    ...
End Class

如果你创建一个C＃WinForms应用程序，构造函数是可见的，所以这让我认为它是一个隐藏它的VB东西。此外，如果您手动将Sub New添加到Form1，它将为您填写一些代码，基本上是“取消隐藏”。

我猜VS看了你的代码并意识到它是System.Windows.Forms.Form的后代，但从技术上讲它是不正确的，因为它没有调用MyBase.New()（因为它不能因为它不存在）所以它只是想猜测。它“知道”以它创建的形式添加对InitializeComponent()的调用，并且它“知道”为您正在查看的表单执行此操作但是它并不打算走遍表单和为所有人做这件事。错误？也许

当您将MoreBellsAndWhistles设置为启动表单时，您从未看到任何一个新按钮，对吧？这就是你如何告诉它更多的VS技巧。

无论如何，整个问题的解决方案是将它添加到两个子类中：

Public Sub New()
    MyBase.New()
    InitializeComponent()
End Sub

并将其添加到Form1：

Public Sub New()
    InitializeComponent()
End Sub