Question

I’ve seen several posts that essentially state that UI components shouldn’t run as a service. I understand the rational that no one can respond to UI events etc. But the fact remains that are are many automation tasks that are only possible with Windows forms.

Here is a couple of great examples:

1. I would like to build a url crawler
   service that makes thumbnails of
   webpages. Currently the only way I
   see to achieve this is to try and
   automate the .Net WebBroswer
   component.

2. Automate the printing of MS-Word
   docs.

Pre-Vista there was some tricks to get around this, but now there is none. My question is why is this the case, and what alternatives does one really have?

Answer 1

Lookup Shatter Attacks and Session 0 Isolation Feature.

Basically if two processes (of different users) share the same desktop, one process can potentially execute whatever code it wants in the other process by sending windows messages, and this was called a Shatter Attack.

There was a lot of discussion whether this was a design bug or not, and post Vista, Microsoft decided to remove any interactive desktop support for services as that was a potential security hole.

As an alternative, you can consider, running your image generation/printing code as a logged in user, who has access to an interactive desktop.