Can ClickOnce update automatically without asking the user?

I have a client who wants a simple installation for a small application for the Windows system tray. They want the application to automatically update without a user request. The application is small, and the update should be minimal in size (most of the business logic and code will be behind the web service).

I paid attention to Microsoft ClickOnce technology, as it seems to be built for such things. My question is, can it be quietly updated backstage without knowing that it is? If not the best way to do this? Is there another technology that works best?

I understand that updating without specifying a user is subjective, but the client is adamant about it.