Firstly, adsense cannot be used in desktop applications, you can search for other ad networks. There are other ad networks, such as amazon associates, etc. You can search for them according to the domains: bank transfer, retail. You can search / contact them for your terms of use on the desktop.
And not all of them will provide you with an API for .Net. If amazon is allowed for desktop use: look at this API
Secondly, wrt technical aspects of WPF. You may have a website created to advertise on your network. Paste the URL into the web browser control in WPF applications. This will work as long as the desktop is connected to the Internet all the time.
If all the doors are closed and you still want to make money from your wpf application, you might consider using the toolbars provided by various providers in your application.
Hope this helps.