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Move canonical knowledge for Microsoft-owned review domains into the Microsoft layer and document the skill/knowledge co-location policy. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Copilot-Session: 2a6ea875-d38e-4f30-aadb-0d606f9be231
28 lines
1.3 KiB
Markdown
28 lines
1.3 KiB
Markdown
---
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bc-version: [15..]
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domain: performance
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keywords: [page-background-task, cue, rolecenter, enqueuebackgroundtask, ui-thread]
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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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# Calculate expensive cues on a page background task
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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Role-center cues and CardPart totals that run `CalcFields`, scans, or HTTP on the UI thread freeze the shell until they finish. Page background tasks exist to return the page immediately and fill the number later. Enqueue mechanics, cancellation, and the read-only child session are covered in `microsoft/knowledge/ui/page-background-tasks.md`. This file is the performance trigger: a cue whose value is not needed to *open* the page must not run on the render path.
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## Best Practice
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Bind the cue to a page variable, enqueue a read-only calculation from `OnAfterGetCurrRecord` (not `OnAfterGetRecord` on a list), and apply the result in `OnPageBackgroundTaskCompleted`. Show a placeholder until then.
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See sample: `page-background-tasks-for-expensive-cues.good.al`.
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## Anti Pattern
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`CalcFields` or a ledger `Count` in `OnOpenPage` / `OnAfterGetCurrRecord` of a CueGroup CardPart with no background task. The Role Center waits on SQL the user may never look at.
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See sample: `page-background-tasks-for-expensive-cues.bad.al`.
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