bcquality/microsoft/knowledge/web-services/api-page-flowfields-must-be-calcfields.md
Michael Dieringer 057e17c202 Add 18 community AL/BC patterns across style, data-modeling, web-services, appsource, breaking-changes, performance, and testing
Contributed by CURABIS ApS, generalized from patterns observed across real AppSource/PTE development. Each article follows the knowledge file format (frontmatter, Description/Best Practice/Anti Pattern, sibling .good.al/.bad.al samples).
2026-09-21 22:24:07 +02:00

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Explicitly Calculate FlowFields on API Pages

Contributions welcome — open a PR to refine or extend this article.

Description

FlowFields are not stored in the database — Business Central computes them on demand. Regular pages trigger that calculation automatically while rendering, but API pages do not. A FlowField referenced in an API page's layout returns an empty value to external consumers unless it is calculated explicitly, producing a silent data gap in OData responses that is easy to miss in review.

Best Practice

Call CalcFields for every FlowField referenced in the page layout from the OnAfterGetRecord trigger, combining multiple fields into a single call.

See sample: api-page-flowfields-must-be-calcfields.good.al.

Anti Pattern

Relying on the implicit calculation that regular pages perform. Any FlowField left out of the CalcFields call returns a blank value to every API consumer with no visible error.

See sample: api-page-flowfields-must-be-calcfields.bad.al.