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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 645349fd-1892-48f3-8a84-db77d6abd1c3
26 lines
1.4 KiB
Markdown
26 lines
1.4 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [event-parameters, signature, backward-compatibility, append, onbefore, integration-event, versioning]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Add new event parameters at the end
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## Description
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Adding a parameter to an existing event publisher changes its signature. For a `local` or `internal` Business or Integration event, subscribers may omit parameters, so a new parameter can be compatible when appended at the end. A public event is also a public procedure that dependent extensions can raise; adding a parameter to it is breaking and requires a new event. Existing parameters must never be renamed, removed, reordered, or have their type changed.
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## Best Practice
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When extending an existing `local` or `internal` Business or Integration event, append the new parameter after all existing ones, including after a trailing `var IsHandled: Boolean` when present. Existing subscribers can continue omitting the new trailing parameter. Create a new event instead when the publisher procedure is public.
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See sample: `add-new-event-parameters-at-the-end.good.al`.
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## Anti Pattern
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Inserting a new parameter before an existing parameter of a `local` or `internal` event, or adding any parameter to a public event. Detection: a changed event signature where a new parameter is not a compatible trailing addition.
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See sample: `add-new-event-parameters-at-the-end.bad.al`.
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