Microsoft MB-820: Microsoft Dynamics 365 Business Central Developer

Last checked October 22, 2026 against the official Microsoft exam page.

1. Question 1Develop AL extensions

   A developer needs to add a new field to the Customer table in Business Central without changing the base application's code. Which AL object should be used?

   1. AA new codeunit with a copy of the table
   2. BA page with no table link
   3. CA report that stores the field
   4. DA table extension object
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   Correct answer: D

   Table extensions add fields to existing tables without modifying the base app, which keeps upgrades safe. A copied codeunit, a report, or an unlinked page does not extend the table itself.

2. Question 2Data and integration

   A developer needs an external system to create sales orders in Business Central through a REST call. Which API approach is recommended?

   1. AEmail the sales orders as attached CSV spreadsheets
   2. BUse the standard API v2.0 endpoints exposed by API pages
   3. CConnect directly to the SQL Server database tables
   4. DUse a screen-scraping script against the web client
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   Correct answer: B

   The standard APIs are the supported integration surface and remain stable across updates. Direct SQL access, emailed spreadsheets, and screen scraping are unsupported and fragile.

3. Question 3Deployment and lifecycle

   An extension is ready to be deployed to a customer's production environment. Which step should come before deployment?

   1. ADelete the existing company data tables and their records first before reinstalling the extension
   2. BTest the extension in a sandbox that mirrors production and validate the upgrade path
   3. CInstall it directly into the production tenant without testing or a rollback plan
   4. DRemove the version number from the app manifest before publishing the build to the production tenant
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   Correct answer: B

   Testing in a production-like sandbox and validating the upgrade path finds issues before they reach customers. Direct installs, deleting data, and removing version numbers increase risk.

4. Question 4Testing and quality

   A developer wants to verify that a new posting extension calculates totals correctly, and to run the test every time the code changes. Which approach is recommended?

   1. ACheck the posted totals manually once in the production environment
   2. BCreate test codeunits with the Test attribute and run them with the test toolkit
   3. CAsk an end user to report calculation errors later through a formal support desk ticket
   4. DTrust the calculation because the code compiled successfully in the development environment
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   Correct answer: B

   Automated test codeunits with the Test attribute, run through the test toolkit, catch regressions each time code changes. Manual production checks, compile success, and user reports detect problems too late.

5. Question 5Extensibility

   A developer wants a new feature to be turned on for some customers only, without a new release. Which Business Central mechanism supports this?

   1. ARenaming the feature flag each week so customers cannot rely on it
   2. BDeleting the feature for everyone and its setup record
   3. CA client screen resolution and display scaling preference in a browser
   4. DFeature management or a setup switch controlled per tenant
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   Correct answer: D

   Feature flags or setup switches enable functionality per customer without releasing separate code. Deleting features, screen resolution, and renaming do not control availability.