bcquality/microsoft/knowledge/events/treat-local-and-internal-events-as-subscriber-contracts.md

bc-version	domain	keywords	technologies	countries	application-area
all	events	local-event internal-event event-subscriber compatibility access-modifier integration-event business-event parameter-name var-parameter appsourcecop	al	w1	all

Treat local and internal events as subscriber contracts

Description

The local and internal access modifiers on Business and Integration event publishers restrict who can raise the procedure; they do not prevent dependent extensions from subscribing. Once shipped, the event name and each existing parameter's name, type/subtype, and value-versus-var passing mode are compatibility contracts even when the publisher is not public. Parameter order is not a subscriber contract because subscribers bind the parameters they use by name. This differs from [InternalEvent], which is module-only except for modules named by internalsVisibleTo.

Best Practice

Preserve a shipped Business or Integration event's identity and every existing parameter's name, type/subtype, and passing mode regardless of the procedure access modifier. AS0025 protects names and types, while AS0063 and AS0077 protect removal and addition of var. New parameters may be added at any position on a local or internal event because subscribers can omit them; public event procedures follow the stricter caller contract described by add-new-event-parameters-at-the-end.

See sample: treat-local-and-internal-events-as-subscriber-contracts.good.al.

Anti Pattern

Renaming or removing an existing parameter, changing its type/subtype, or adding/removing its var modifier because the event publisher procedure is local or internal. AppSourceCop checks these subscriber-breaking changes because dependent event subscribers can still bind to the event. Reordering unchanged parameters, or inserting a new parameter among them, is not this anti-pattern.

See sample: treat-local-and-internal-events-as-subscriber-contracts.bad.al.