Customizing standard processes in Dynamics 365 Finance and Operations has evolved significantly. Gone are the days when overlayering was the norm. Today, we work with event handlers - a cleaner, upgrade-safe way to extend standard logic without touching Microsoft’s base code.
In this post, I’ll break down how event handlers work, when to use them, and walk you through a real-world example that illustrates how powerful (and easy) they are to implement.
Why Event Handlers Deserve Your Attention ?
As developers and technical consultants, we’re often tasked with extending standard business logic. Event handlers let us do that without modifying the original codebase. This ensures:
- No conflicts during platform upgrades
- Better code separation for long-term maintenance
- Compliance with Microsoft's One Version policy
Mostly used types of event handlers
Depending on your use case, there are different handler types available:
| Event Type | Purpose |
|---|---|
| Pre-event | Executes before the standard method – ideal for validations |
| Post-event | Executes after the method – great for additional processing |
| OnModified, OnValidated | Used for form field-level triggers |
| DataEventHandlers | Fire during insert/update/delete events on tables |
Use Case: Auto-Generating Vendor Codes
Let’s say your client needs vendor records to be assigned a unique code automatically when a new vendor is created. The standard VendTable insert method doesn’t do this out-of-the-box.
Instead of overlayering the base method (which is a no-go in today’s world), we’ll attach a post-event handler.
class VendTableEventHandler
{
[PostHandlerFor(tableStr(VendTable), tableMethodStr(VendTable, insert))]
public static void VendTable_PostInsert(XppPrePostArgs args)
{
VendTable vendTable = args.getThis() as VendTable;
if (!vendTable)
return;
vendTable.selectForUpdate(true);
vendTable.VendCode = VendTableEventHandler::generateVendorCode(vendTable.RecId);
vendTable.doUpdate();
}
private static str generateVendorCode(RecId recId)
{
return strFmt("VEND-%1", recId);
}
}
Now, every time a vendor is created, this handler fires after the insert and assigns a custom vendor code like VEND-123456.
Tips to Keep in Mind
- Keep event logic focused - Don’t clutter handlers with business rules. Move complex logic into helper or service classes.
- Naming matters - Use consistent names like
VendTableEventHandlerso future developers can easily trace logic. - Avoid assumptions about execution order - If multiple handlers exist, the order isn’t guaranteed — so design your logic to be independent.
When to Use Event Handlers vs. Chain of Command
Both are powerful, but they serve different purposes:
| Use case | What to use ? |
|---|---|
| Working with public table/form methods | Event Handler |
| Modifying protected business logic (services, controllers) | Chain of Command |
| Handling table-level inserts/updates | DataEventHandler |
| UI interaction (field validations) | Form event methods |
Conclusion
Understanding how and when to use event handlers is essential for any D365 F&O developer or architect. Not only does it keep your codebase cleaner and upgrade-ready, but it also aligns with how Microsoft expects us to extend their platform moving forward.
If you’re still relying on overlayering, it’s time to re-think your approach. With just a few lines of code, event handlers give you the flexibility you need — without the headaches that come with platform updates.
That's all for now. Please let us know your questions or feedback in comments section !!!!
