How to add a WiX custom action that happens only on uninstall (via MSI)?

Question

I would like to modify an MSI installer (created through WiX) to delete an entire directory on uninstall.

I understand the RemoveFile and RemoveFolder options in WiX, but these are not robust enough to recursively delete an entire folder that has content created after the installation.

I noticed the similar Stack Overflow question Removing files when uninstalling WiX, but I was wondering if this could be done more simply using a call to a batch script to delete the folder.

This is my first time using WiX, and I'm still getting the hang of custom actions. What would be a basic example of a custom action that will run a batch script on uninstall?

Answer 1

EDIT: Perhaps look at the answer currently immediately below.

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This topic has been a headache for long time. I finally figured it out. There are some solutions online, but none of them really works. And of course there is no documentation. So in the chart below there are several properties that are suggested to use and the values they have for various installation scenarios:

So in my case I wanted a CA that will run only on uninstalls - not upgrades, not repairs or modifies. According to the table above I had to use

<Custom Action='CA_ID' Before='other_CA_ID'>
        (NOT UPGRADINGPRODUCTCODE) AND (REMOVE="ALL")</Custom>

And it worked!