.net 如何更改自定义控件的默认大小

我不熟悉在VB.NET中添加自定义控件。 我想要一个类似PictureBox的控件，该控件具有默认大小和图片，两者最好都不可更改。
我首先向项目中添加了一个新类，然后添加了以下代码：

Public Class CustomControl
Inherits Windows.Forms.PictureBox
    Protected Overrides Sub OnCreateControl()  
        MyBase.OnCreateControl()
        Me.Image = Global.Mazerino.My.Resources.Resources.ControlImage           
        MyBase.Size = New System.Drawing.Size(20, 20) 'Also tried setting Width and Height 
                                                      'properties instead. 
    End Sub
End Class

我执行项目，关闭，然后添加控件；图像已添加，但大小未更改。默认控件的大小为150,50

因此，我添加了以下代码：

Private ControlSize As Size = New Size(10, 10)
Overloads Property Size As Size        
    Get
        Return ControlSize
    End Get  

    Set(value As Size)
    'Nothing here...
    End Set
End Property

但它也不起作用，所以我试着：

Shadows ReadOnly Property Size As Size
    Get
        Return ControlSize
    End Get
End Property

在将控件添加到窗体时，它起作用，但当我执行该程序时，我得到以下错误：“属性大小仅为只读”。双击时，表单设计中会出现以下代码：

Me.CustomControl1.Size = New System.Drawing.Size(10, 10)

这导致我将属性更改为读写，但当我再次这样做时，控件大小保持在150,50

那么，如何将默认大小设置为特定大小，而不在将控件添加到表单时遇到问题呢

Public Class CustomControl : Inherits Windows.Forms.PictureBox

    Private ReadOnly INMUTABLE_SIZE As Size = New Size(20, 20)

    Public Shadows Property Size As Size
        Get
            Return INMUTABLE_SIZE
        End Get
        Set(value As Size)
            MyBase.Size = INMUTABLE_SIZE
        End Set
    End Property

    Protected Overrides Sub OnSizeChanged(e As System.EventArgs)
        MyBase.Size = INMUTABLE_SIZE
        MyBase.OnSizeChanged(e)
    End Sub

End Class

---

您是否尝试过设置最小和最大尺寸

Public Class CustomControl Inherits Windows.Forms.PictureBox
     Protected Overrides Sub OnCreateControl()  
         MyBase.OnCreateControl()
         MyBase.SizeMode = PictureBoxSizeMode.StretchImage
         Me.Image = Global.Mazerino.My.Resources.Resources.ControlImage           
         MyBase.Size = New System.Drawing.Size(20, 20) 'Also tried setting Width and Height 
                                                       'properties instead.
         MyBase.MaximumSize = New Size(20,20)
         MyBase.MinimumSize = New Size(20,20) 
     End Sub
End Class