Best Way to Create an Installation that only Upgrades?

My company is creating a cheaper version of our product that will only upgrade from an older version. To accomplish this, I would like to create an installation that will ONLY upgrade from a previous version. It will not install the full product. Is there a straightforward way to do this? I have considered: 1) Creating a custom action that checks the registry for the old version first; 2) Creating a patch/hotfix installation Is there a better method to do this? If not, are there any large pitfalls and drawbacks to these methods? Method #2 seems like the easier method, but this is a pretty big upgrade (though not a "major upgrade," from a technical standpoint). I don't like the appearance of a hotfix when the upgrade is no such thing.

By 开发者_开发问答the way, I am writing the installer in WiX.

This really boils down to one question: does the upgrade move or remove files?

If it does, you need a major upgrade. In this case just make sure that your new version uses the same Upgrade Code as the old one. Windows Installer will take care of the old version removal.

To prevent the package from performing a standalone installation you can use an upgrade rule. You can define a rule which detects older versions and saves them in an installer property. This property can then be used as a launch condition.

If the upgrade doesn't need to remove files, you can use a patch. In this case you don't need to worry about standalone installations.