Disposing members of an instance of an unknown type

This is for a program that has a built-in script system (using CodeDom), and requires the objects that were created by the script to be disposed before updating/re-compiling the script, in order to stop the execution of the older assembly.

I'm trying to make a generic method to dispose an instance of any class, so that scripters don't need to implement IDisposable.

Let's say the scripter created a class, with unknown contents, that may not implement IDisposable.
Like this:

vb Code:

Public Class foo
    Dim obj1 As New managedType1()
    Dim obj2 As New managedType2()
    Dim var1 As unmanagedType1
End Class

vb Code:

Dim myFoo As New foo

How to dispose myFoo?

I've tried it this way (with a class that has StructLayout attribute):

vb Code:

Public Shared Sub DisposeObj(ByVal obj As Object)
        If TypeOf obj Is IDisposable Then
            CType(obj, IDisposable).Dispose()
            Exit Sub
        End If
 
        Dim typeOfObj As Type = obj.GetType()
        If typeOfObj.StructLayoutAttribute Is Nothing Then Exit Sub
 
        Dim gch As GCHandle = GCHandle.Alloc(obj)
        Dim offset As Integer
        Dim memberObj As Object
 
        'try to dispose the members of this class
        For Each member As Reflection.MemberInfo In typeOfObj.GetMembers(Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance Or Reflection.BindingFlags.DeclaredOnly)
            offset = Marshal.OffsetOf(typeOfObj, member.Name).ToInt32
            memberObj = GCHandle.FromIntPtr(New IntPtr(GCHandle.ToIntPtr(gch).ToInt32 + offset)).Target
 
            DisposeObj(memberObj)
        Next
    End Sub

But line 17 returns obj. I know this wasn't even supposed to work, because the offset doesn't tell where the member instance is allocated.

Any other ideas?