Having an issue with WIX upgrade

Question

Having an issue with WIX installer upgrade. Previously we had 2 version of installers 1 for per-machine and another for per-user.

Currently we have developed a dual mode

Answer 1

Per-user installs allow the installation of the same product multiple times for different users - and in different versions too. This makes upgrades and patches rather difficult to deal with, and I dislike this per-user concept altogether. I prefer to set the installer per-machine as standard. I don't feel that much is lost in functionality, but a lot is gained in managability. Though this is not an answer to your question, it is worth pointing out that per-user installs is a flawed concept - at best.

I don't know if it is an option to set your installer per-machine, but I found a way to migrate installs from per-user to per-machine automagically by using Installshield and its custom ISSetAllUsers custom action. The procedure is described here: windows Installer - uninstalling previous version when the versions differ in installation policy (per-user, per-machine)

Wix does not feature such a custom action as far as I know, but you could write your own custom action using the Win32 API call ::MsiEnumRelatedProducts() as described by Rob Mensching here: how to change from per user to all user installation?

Here is a similar post for reference: How can a perUser installation program deal with a perMachine older version of the program?

Here is a blog describing (further) issues with per-user installs: Understanding “Per-User” or “Per-Machine” context for application Setup packages.

Let me add a couple of further comments:

• You can have per-user settings without a per-user install. This is no problem, just have the application set up the userprofile on launch. I prefer to install all resource files and settings per-machine and have the application copy them to each user for first launch initialization. This ensures that user settings are not entangled with your MSI at all.
• It is rare to maintain two separate versions of the same product at the same time - hence users are all likely to use the same version of the product. Per-user is just more headache in this perspective.
• The upgrade and patching logic involved in per-user installer scenarios beats me - it just doesn't make any sense to me. If there is a per-machine install already, does a per-user install make sense to you? Does this install the application one more time?
• If per-user installs are still important, perhaps you can try ClickOnce (if it still works). Quote from Wikipedia: "...ClickOnce-deployed applications are considered 'low impact', in that they are installed per-user, not per-machine. No administrator privileges are required to install one of these applications. Each ClickOnce application is isolated from the others. This means one ClickOnce application is not able to 'break' another.". Per-user installs make more sense if they are hooked up to auto-updating and web-deployment.