NAV2013R2: How to load XMLPort from C#

Hi, everyone,
I used this link to create web-service which exports items through XML port: http://kauffmann.nl/index.php/2011/01/15/how-to-use-xmlports-in-web-services-1/#codesyntax_1

I loaded result from using DataGrid. That works fine - I can see the list of items.

However, I would like to load the results into an XMLDocument so I can then read through it and do what I need. I am not very good with C#, so I need an advise, how can I achieve it?

Thanks in advance.