How to implement WiX installer upgrade?

Question

At work we use WiX for building installation packages. We want that installation of product X would result in uninstall of the previous version of that product on that machi

Answer 1

The Upgrade element inside the Product element, combined with proper scheduling of the action will perform the uninstall you're after. Be sure to list the upgrade codes of all the products you want to remove.

Note that, if you're careful with your builds, you can prevent people from accidentally installing an older version of your product over a newer one. That's what the Maximum field is for. When we build installers, we set UpgradeVersion Maximum to the version being built, but IncludeMaximum="no" to prevent this scenario.

You have choices regarding the scheduling of RemoveExistingProducts. I prefer scheduling it after InstallFinalize (rather than after InstallInitialize as others have recommended):

This leaves the previous version of the product installed until after the new files and registry keys are copied. This lets me migrate data from the old version to the new (for example, you've switched storage of user preferences from the registry to an XML file, but you want to be polite and migrate their settings). This migration is done in a deferred custom action just before InstallFinalize.

Another benefit is efficiency: if there are unchanged files, Windows Installer doesn't bother copying them again when you schedule after InstallFinalize. If you schedule after InstallInitialize, the previous version is completely removed first, and then the new version is installed. This results in unnecessary deletion and recopying of files.

For other scheduling options, see the RemoveExistingProducts help topic in MSDN. This week, the link is: http://msdn.microsoft.com/en-us/library/aa371197.aspx