I faced with the problem in my WIX installer: how can I stop specific IIS application pool during repair, change or update? Description: Deliver and deploy Web Application, run repair. Dialog appears that says that w3wp process locks files. In addition, because of requirements I cannot just hide that message and I cannot change Web Application.
What I tried to do:
Please, help me overcome this issue.
You can use quiet execute custom action to shell out to appcmd to stop an app pool. You are right though, you wouldn't always be elevated prior to InstallValidate.
https://technet.microsoft.com/en-us/library/cc732742(v=ws.10).aspx
I suspect this is probably a false alarm and will resolve itself later in the installer. I would look at the various was to suppress this dialog. Maybe this would help:
WiX: Avoid showing files-in-use dialog and just prompt for reboot at end of install