限制严格关闭VB.NET版

嗨,我正在探索如何实现一些访客模式,而不是所有的装饰访问方法。现在我发现我可以用严格的选项VB.NET版但也有一些副作用。我有一组从基类形状继承的形状类。假设我们有以下接受形状的类:

Public Class ShapeAcceptor 
    Public Sub New()
      MyBase.New
    End Sub
    Public Sub AcceptShape(s as Shape)
      AcceptAny(s)
    End sub
    Private Sub AcceptAny(o as Object)
      Accept(o)
    End sub

    Private Sub Accept(byval s as Shape)
      Console.writeLine("Shape")
    End Sub 
    Private Sub Accept(byval s as Square)
      Console.WriteLine("Square")
    End sub
    Private Sub Accept(byval s as Circle)
      Console.writeLine("Circle")
    End Sub
    Private Sub Accept(byval s as Triangle)
      Console.writeLine("Triangle")
    End Sub  
  End Class

Public Class Application
    Public Shared Sub Main()
      Dim acceptor as new ShapeAcceptor
      Dim env as new Envelope
      For Each s  as Shape in env.Items
        acceptor.AcceptShape(s)
      Next
      acceptor.AcceptShape(new NotAShape())
     End Sub
  End Class