WIX: Saving off user data files during major upgrade

My application runs as a Windows service. During normal execution, some data files are generated in a "data" directory that I create with my WIX install. During an upgrade, I would like to move/migrate those files to the same data dir in the upgraded installation. However, I am running into issues. I am using the "MajorUpgrade" tag as follows:

I tried scheduling later in the process(afterInstallFinalize), but that runs into issues with the service having locks on files during the upgrade. I have combed Stack Overflow and google, and it seems that no one else is describing my 开发者_JS百科scenario. Others have default *.ini files, that the user can potentially edit. However, in my case, it should always be safe to migrate the files, as there are no defaults. They are simply data files that need to be migrated.

I thought I could possibly do this via a custom action, but was not sure how to do it.

Any suggestions would be very much appreciated.

Edit: Apparently using "afterInstallFinalize" works fine for me, i.e. data files are migrated, as long as the user does not change the path during upgrade. If I change the path during upgrade, I get warnings about files being locked, and asking to stop the app using the files. However, it ends up not migrating the files in that case.

Ultimately, I solved my own issue by simply overriding the default dialog behavior, and changing the flow such that on upgrade, I skip over the "InstallDirDlg".