Silent updates on Mac

I have written silent updates on Windows. I would have an update service running which would check with a web service to see if there are any updates and if so, copy the dll to the location. I am using Mono to write my application on Mac. The entire bundle gets cop开发者_如何学运维ied to the folder. So how can I selectively copy only certain dlls. Should I always delete the old version and copy the new version of the software.

Don't write your own. Take a look at Sparkle. It has become the de-facto standard for updates for third-party (non-Apple) apps on Mac OS X.