server.transfer and context handler

[segue]

When I use server.transfer to transfer properties between two asp.net pages
in a third party .NET 2.0 project,
I can’t extend one form to another by having the original page seen as part
of the project (using the context handler technique):

(There is no projectname.firstpage to import).

Imports Enterprise.editCustomer

Dim sourcepage As editCustomer

Protected Sub Page_Load(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Me.Load

If Not Page.IsPostBack Then

sourcepage = CType(Context.Handler, editCustomer)
getsalesinfo(sourcepage.cust)

Thanks for any suggestions as to what I could try, I've played around with
inherits in the aspx and tried copying other things the third party project
is using like master page directives, etc.. The above works outside of this
particular 3rd party project.

Regards