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Lead with a complete plugin quick start and add task-oriented usage, troubleshooting, customization, and contribution guides. Preserve the broader plugin framing, correct conflicting contract guidance, support Agents folder reviews, and align repository validation. Convert existing sample references to clickable links without changing knowledge rules. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
26 lines
2.5 KiB
Markdown
26 lines
2.5 KiB
Markdown
---
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bc-version: [all]
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domain: events
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keywords: [ishandled, carry-over, loop-iteration, onbefore, reset, integration-event, control-flow, false-positive]
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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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# Reset IsHandled before publishing only when its value can carry over
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## Description
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A routine that raises an `OnBefore…` integration event with a `var IsHandled: Boolean` parameter passes that variable by reference, so a pre-existing `true` can affect the following control flow. AL [automatically initializes Boolean variables to `false`](https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/devenv-al-variables#initialization), so a freshly declared local Boolean passed to one event exactly once per procedure invocation is already deterministic. Initialization does not repeat for each loop iteration: a local declared outside a loop can carry `true` from one iteration to the next even when the source contains only one textual event raise. Outside a loop, reaching a later raise after `if IsHandled then exit;` also proves the value is `false`, provided that early exit is semantically correct and does not skip required downstream events.
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## Best Practice
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Reset `IsHandled := false;` before a raise only when the value might otherwise carry over as `true`: the same variable is reused after an earlier raise without a control-flow proof that it is false, a raise is re-entered by a loop, the value comes from an input parameter, field, or global, or earlier code seeds it. Prefer separate fresh locals when independent event seams need independent handled state. A reset on a guaranteed-false fresh local used by one non-looping raise, or before a later raise reached only after a semantically valid `if IsHandled then exit;`, can be retained for readability, but its absence is not a correctness finding.
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See sample: [`reset-ishandled-only-when-the-value-can-carry-over.good.al`](reset-ishandled-only-when-the-value-can-carry-over.good.al).
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## Anti Pattern
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Raising `OnBeforeX(…, IsHandled)` when the variable can still be `true` from an earlier raise, an earlier loop iteration, or another source, so the publisher call starts with stale state. Do not match a single non-looping raise using a fresh local Boolean, or a later raise reached only after a semantically valid `if IsHandled then exit;` proves the value is false.
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See sample: [`reset-ishandled-only-when-the-value-can-carry-over.bad.al`](reset-ishandled-only-when-the-value-can-carry-over.bad.al).
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