bcquality/microsoft/knowledge/events/preserve-onafter-execution-when-ishandled-skips-the-body.md

bc-version	domain	keywords	technologies	countries	application-area
all	events	ishandled onafter event-pairing control-flow guard integration-event side-effects	al	w1	all

Preserve OnAfter execution when IsHandled skips the body

Description

A routine that exposes both an OnBefore… event (with var IsHandled) and a paired OnAfter… event has a subtle trap. The common if IsHandled then exit; guard returns from the whole routine, so when a subscriber handles the OnBefore the OnAfter event never fires. Subscribers that depend on OnAfter — logging, downstream integration, dependent updates — then silently stop running whenever some other extension overrides the body. The fix is to skip only the default body, not the routine, so the OnAfter still publishes. The two seams are independent: overriding the work should not cancel the notification that the work happened.

Best Practice

Wrap only the default work in if not IsHandled then begin … end; and keep the OnAfterX(…) raise after that block, outside the guard, so it always fires regardless of whether a subscriber handled the OnBefore. This keeps the override seam and the after-notification independent, which is what subscribers expect.

See sample: preserve-onafter-execution-when-ishandled-skips-the-body.good.al.

Anti Pattern

Guarding with if IsHandled then exit; and placing the OnAfterX raise later in the same routine, so handling the OnBefore short-circuits the whole procedure and the OnAfter event is skipped along with the body. Detection: an if IsHandled then exit; in a routine that also raises a paired OnAfter… event after that point.

See sample: preserve-onafter-execution-when-ishandled-skips-the-body.bad.al.