あとで書くけど。
WithEventsはこんなしくみ。
Friend Overridable Property Button1 As Button
Get
Return Me._Button1
End Get
Set(ByVal WithEventsValue As Button)
If (Not Me._Button1 Is Nothing) Then
RemoveHandler Me._Button1.Click, New EventHandler(AddressOf Me.Button1_Click)
End If
Me._Button1 = WithEventsValue
If (Not Me._Button1 Is Nothing) Then
AddHandler Me._Button1.Click, New EventHandler(AddressOf Me.Button1_Click)
End If
End Set
End Property