X++ & Microsoft D365 standards

Since Dynamics 365 F&O 7.0 (formerly AX 7), Microsoft replaced over-layering with an extension model. Microsoft core code can no longer be modified directly; you add your business logic using 3 official patterns.

Skalp AI uses exclusively these 3 patterns. No over-layering is ever generated, ensuring your developments survive One Version release waves (twice a year) and major upgrades without human intervention.

Pattern choice depends on the business need: extend a table → Table Extension; modify existing behavior → Chain of Command; react to an event → Event Handler. Skalp AI selects the most appropriate pattern and documents it in the Pull Request comment.

Chain of Command (CoC) lets you extend an existing method without replacing it. You wrap the standard Microsoft method with your own logic before and/or after the original call. It is the recommended pattern to change the behavior of a standard class, table or form.

Skalp AI generates CoC extension classes when you need to add a validation, calculation, side-effect or transformation around an existing method. Code follows the [ExtensionClassName]_Extension naming with attribute [ExtensionOf(classStr(StandardClass))].

Typical example: add a consistency check to PurchOrder validation before save, without touching Microsoft code. The ticket generates a wrapper class that calls next then adds your business check.

Event handlers subscribe to pre- or post-method events published by standard Microsoft objects. When the event fires (onValidatingWrite, onInsert, onClicked, etc.), your handler runs.

Skalp AI generates event handlers when the business need is asynchronous by nature: trigger an integration, send a notification, feed an audit log, or react to a status change. Code is packaged in a static class with [SubscribesTo(...)] attributes.

Key benefit: an event handler is fully decoupled from the main code. It can be disabled without impact on the standard flow. Ideal for optional features or module-specific functionality.

Extension classes let you add fields, methods, controls or values to a standard Microsoft entity without duplicating it. It is the simplest pattern: extending the object definition rather than its behavior.

Skalp AI generates Table Extensions to add business fields (profit center, GDPR flag, external reference…), Form Extensions to adapt screens (tab addition, conditional hiding, custom button), and Enum Extensions to extend business value lists.

The extension automatically follows the Microsoft naming convention: .Extension suffix, business prefix consistent with your model (e.g. SKL_CustTable_Extension), systematic [ExtensionOf(...)] attribute.

Over-layering (direct modification of Microsoft code via the SLN, USR layer, etc.) was the norm until AX 2012. Microsoft officially deprecated it since D365 F&O 7.0 and made it technically impossible in cloud environments from 10.0.

Skalp AI NEVER generates over-layering, even on migration from AX 2012. Any AX 2012 over-layered code is systematically rewritten in an extension pattern (CoC, event handler or extension class as appropriate) during migration.

Practical consequence: your Skalp AI code survives One Version release waves without intervention. You avoid the major technical debt that slows most D365 customers during upgrades.

Microsoft ships One Version as successive release waves (typically 8 waves per year, with intermediate service updates). Each wave can introduce method signature changes, deprecations or new events.

Skalp AI generates code that follows the current public contracts documented by Microsoft. When a signature changes in a release wave, your CoC extensions may need a minor update (signature change) — automatically detected during CI build.

For each release wave, Microsoft publishes an "upgrade analyzer" that flags impacted extensions. If one of your Skalp-AI-generated extensions is impacted, you can submit an update ticket (typically €200 to adapt to the new signature, sometimes requalified as bonus without billing).

Statistically, fewer than 5% of extensions are impacted per release wave. The ratio improves with extension patterns which are the long-term Microsoft-supported path.