vb.net is it possible to extend a system class?

Question

I want to add a function to System.IO.Path Class.

The Problem is Path is NotInheritable.

So doing that is impossible:

Imports System.IO

Public Class Path : Inherits System.IO.Path

End Class

Answer 1

You can use Extension Methods. Those seem to be the functions of the extended class, but there is no real connection between them. They do make programming a bit more convenient though.
http://msdn.microsoft.com/en-us/library/bb384936.aspx

Update: Let's see an example. Note that these are snippets from 3 files.

'Noninheritable baseclass
Public NotInheritable Class BaseClass
    Function f()
        Return 42
    End Function
End Class

'Extension
Imports System.Runtime.CompilerServices
Module ExtModule
    <Extension()>
    Public Sub Print(ByVal bc As BaseClass)
        Console.WriteLine(bc.f())
    End Sub
End Module

'Usage
Sub Main()
    Dim bc As BaseClass
    bc = New BaseClass()
    bc.Print() 'Calling the extension method
End Sub

And it says 42.