There are five triggers for each Field control. The Container, Group, and Part controls do not have associated triggers. The following screenshot shows the Page Control triggers:

The guideline for the use of these triggers is the same as the guideline for Page triggers--if there is a choice, don't put C/AL code in a Control trigger. Not only will this make our code easier to upgrade in the future, but it will also make it easier to debug, and it will be easier for the developer following us to decipher our changes.