MSI patch - file creation date

Question

I want to patch an msi install. If the time stamp of an otherwise identical file is different in the baseline msi vs the current msi, will that be detected as a changed file and consequently be included in the resulting msp file? If yes, is there a way to avoid this?

The specific scenario is the following: Suppose baseline msi has dlls A and B and is built on date X - during the build process all dlls are generated. The new msi has dll A which changed and dll B which is the same and it is build on date Y - dlls A and B will also be build and have timestamp Y. Will B be included in the differencing msp file? (I use wix)

Answer 1

Windows Installer will generally not replace a DLL that shares the same version as its predecessor (and thus I'd guess WiX's build may exclude it). However if your DLL files are unversioned and you're not using companion files that have versions, the dates on the already-installed file can get involved in unfortunate ways: the file can be detected as user data and be excluded from replacement. See File Versioning Rules for details, along with its link to Default File Versioning.