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

In the newest versions (from the 3.5.1315.0 beta), you can use the MajorUpgrade element instead of using your own.

For example, we use this code to do automatic upgrades. It prevents downgrades, giving a localised error message, and also prevents upgrading an already existing identical version (i.e. only lower versions are upgraded):