Recommendations for detecting updates to prerequisites in Click once app

I have a 开发者_运维知识库click once app that uses SQL CE 3.5, which is set as a pre-requisite.

When the install happens Click once, downloads the prerequisites, including SQLCE, installs them, then installs my software and all works - Fantastic!

Now, I perform an update to my application, which requires that SQL CE 3.5 SP2 is needed.

As the application is already installed, when the icon is started on the users pc, my updated code is downloaded and installed ---- and then the app falls over because functions in SP2 are not available.

I can detect in code if the prerequsite or SP2 is there, using the registry... and then link to an extracted version of the installer to download and install that SP2, but its all a bit clunky.... Anyone have a better idea, maybe using the existing prerequiste check in click once?

If I was installing SQLCE, I would include the dll's locally rather than using a prerequisite, which would give me complete control over what version is used.

http://robindotnet.wordpress.com/2010/02/28/how-to-deploy-the-sqlserver-compact-edition-software-locally/