Public Class Form1
     Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
          Dim f As New Foo
          Dim b As New Bar
          FooBarTest.Test(f)
          FooBarTest.Test(b)
     End Sub
End Class
Public Interface foobar
     Function gs()
End Interface
Public Class Foo
     Implements foobar
     Public Function gs() As Object Implements foobar.gs
          Return "Foo"
     End Function
End Class
Public Class Bar
     Implements foobar
     Public Function gs() As Object Implements foobar.gs
          Return "Bar"
     End Function
End Class
Public Class FooBarTest
     Public Shared Sub Test(ByVal o As foobar)
          FooBarTest.privateTest(o)
     End Sub
     Private Shared Sub privateTest(ByVal o As Foo)
          MessageBox.Show(o.gs & "-Bar")
     End Sub
     Private Shared Sub privateTest(ByVal o As Bar)
          MessageBox.Show("Foo-" & o.gs)
     End Sub
End Class