MSI Major Upgrade overwriting rules

Question

I think I read it somewhere, but couldn\'t find the source now and can\'t confirm it: when install(Major upgrade) a newer version from MSI, if the file has been modified (ei

Answer 1

My guess is that the change in behavior is because you have moved RemoveExistingProducts early in the InstallExecuteSequence.

A major upgrade is essentially running an uninstall of the original product, and then a reinstall of the new one. If RemoveExistingProducts is late in the InstallExecuteSequence - and component referencing is done correctly - the existing product is not uninstall first, but its "leftover" components are removed after installing the new product. It works like a "diff" if you like. This will preserve installed files on disk that are not removed in the new version. I hope that was comprehensible - a lot at once, and rushed.

Here is a thread that deals with ensuring unversioned files get updated during an update: Forcing an upgrade of a file that is modified during its initial installation