Web service using extension codeunit - Still need help

I have made a nav web service with extension codeunit, but I can not see the methods of the extension codeunit when I call it from .net.
I have verified the web service availability, and tested the service in .net before I added the extension codeunit and it worked fine.
Any suggestions on this issue?
The code unit calls XMLPort and and saves a XML file to the users hard drive.

I have added a new method to my codeunit and I can call it form .net app.
But why can’t I see the method that should create XML?
I am little bit confused now.
How else can I create this XML file and save it on users computer?