Events ovveride

Without baseMethod - event subscription → base runs automatically

With baseMethod - override → you must call base manually

​@mos11 

Signature 1:  Override (replaces the base):

protected void _(Events.RowSelected<ARInvoice> e, PXRowSelected baseMethod) { }

You are taking full control of the process. The baseMethod contains all the existing logic that was already there. If you don’t call  baseMethod(e.Cache, e.Args), that existing logic will not run.
So it’s up to you whether to run it or skip it.

 

Signature 2 :  Append

protected void _(Events.RowSelected<ARInvoice> e) { }

Your method is added to the list of existing handlers.
It runs together with them, not instead of them.
You don’t control the whole process, so there’s nothing you need to call or skip ,  everything runs automatically.

For most customization work, we do generally,  use the no-parameter signature unless you specifically need to suppress or conditionally skip existing base logic. The baseMethod pattern is powerful but risky,  if you forget to call it, you can silently break base Acumatica behavior in ways that are hard to debug.

Hope this info helps!