What Are Plugins and Why Do We Need Them?
Dynamics 365 plugins are custom business logic components that run on the server-side within the event framework. They act as event handlers that execute in response to specific data operations like Create, Update, Delete, or custom actions. Plugins enable you to extend Dynamics 365's out-of-the-box functionality without modifying the core platform. official plugin documentation.
Think of plugins as interceptors that sit between the user's request and the database transaction. When a user creates an account record, your plugin can validate data, enrich it with information from external systems, trigger workflows, or prevent the operation entirely based on business rules.
Common Use Cases
- Data Validation: Enforce complex business rules that exceed standard field validation
- Data Enrichment: Auto-populate fields based on calculations or external data sources
- Integration: Sync data with external systems like ERP, marketing platforms, or legacy databases
- Automation: Trigger complex multi-step processes that can't be handled by workflows alone
- Auditing: Create custom audit trails or compliance logging beyond standard features
The Event Execution Pipeline
The event execution pipeline is the heart of plugin architecture. Every data operation in Dynamics 365 passes through a series of stages, and plugins can register on specific stages to intercept and modify the operation. event framework.
Pipeline Stages
Stage 10: PreValidation
Executes outside the database transaction. Best for operations that don't require rollback capability or when you need to fail fast before expensive operations. Use this for lightweight validation or data that won't be part of the transaction.
Stage 20: PreOperation
Executes inside the database transaction, before the main operation. This is where most business logic lives. You can modify the target entity, perform calculations, or call external services. Changes made here are included in the transaction.
Stage 30: MainOperation
Reserved for internal platform use. Developers cannot register custom plugins on this stage.
Stage 40: PostOperation
Executes inside the database transaction, after the main operation completes. Use this when you need the record's GUID (for Create operations) or when you need to perform operations based on the final committed values. Ideal for triggering related record updates or calling external systems.
Understanding Messages
Messages represent the specific operations you're intercepting. Common messages include Create, Update, Delete, Retrieve, RetrieveMultiple, and many specialized operations like Merge, Assign, or SetState. entity message reference.
Each message has a specific context and available data. For example, the Create message provides access to the target entity being created, while Update provides both the target (changed attributes only) and the full record through images.
Critical Message Considerations
- Update Message: Only contains modified attributes in the Target. Use images to access unchanged fields.
- Delete Message: Receives an EntityReference in the Target, not a full Entity object.
- Custom Actions: Can have input/output parameters accessed through context.InputParameters and context.OutputParameters.
- Filtered Attributes: Can register a plugin to fire only when specific attributes change, reducing unnecessary executions.
Pre-Image and Post-Image: Your Time Machine
Entity images are snapshots of the record at different points in the pipeline. They're absolutely critical for Update scenarios where you need to compare old and new values or access fields that weren't modified. entity images and execution context.
Pre-Image (Before Image)
A snapshot of the record before the operation. Available in PreOperation and PostOperation stages for Update and Delete operations. Use pre-images to:
- Compare old vs. new values to detect specific changes
- Access fields that weren't included in the Update message
- Preserve original values for audit or rollback logic
- Make decisions based on the previous state
Post-Image (After Image)
A snapshot of the record after the operation. Only available in PostOperation stage. Contains the merged state of all changes including defaults, calculated fields, and system-populated values. Use post-images to:
- Access the complete final state of the record
- Get system-generated values like CreatedOn or ModifiedBy
- Read calculated or rollup field values
- Trigger logic based on the committed state
⚠️ Performance Tip:
Always select specific attributes when registering images instead of retrieving all columns. Each image requires a database query, so minimize the performance impact by requesting only what you need.
Synchronous vs. Asynchronous Execution
Synchronous Plugins
Execute immediately and block the user's operation until completion. The user interface shows a loading indicator and waits for your plugin to finish. Synchronous plugins run in the same database transaction as the triggering operation.
When to use Synchronous:
- Data validation that must prevent the operation
- Modifications to the current operation's data
- Operations that must complete before the user proceeds
- Quick operations (under 2 seconds execution time)
Limitations:
- 2-minute timeout limit before automatic termination
- Poor user experience if operations are slow
- Can't commit partial work - all or nothing transaction
Asynchronous Plugins
Execute in the background using the System Job (AsyncOperation) queue. The user's operation completes immediately, and the plugin processes separately. Failed async plugins can be automatically retried.
When to use Asynchronous:
- Long-running operations (reports, bulk updates, external API calls)
- Non-critical operations that can tolerate delays
- Integration scenarios where immediate response isn't required
- Operations prone to transient failures that benefit from retry logic
Considerations:
- No guaranteed execution time - depends on queue depth
- Can't modify the triggering operation's data
- Must handle cases where the original record has changed or been deleted
- PreImage/PostImage are persisted but consume storage
Plugin Registration Best Practices
Execution Order and Ranking
When multiple plugins register on the same message and stage, execution order is determined by the Execution Order (Rank) value. Lower numbers execute first. Always document why specific ordering is required. Plugin Registration Tool.
Filtering Attributes
For Update messages, always specify filtered attributes to prevent unnecessary plugin executions. Your plugin only fires when those specific attributes are modified, dramatically improving performance.
Deployment
- Use Isolation Mode: Sandbox (required for online environments)
- Sign assemblies with a strong name key
- Deploy via Solutions for proper ALM and version control ALM guidance
- Test in Development → UAT → Production progression
- Never deploy directly to production without testing
Error Handling and Security
Always throw InvalidPluginExecutionException for expected errors with user-friendly messages. Let unexpected exceptions bubble up naturally - they'll be logged automatically. Use the tracing service for debugging, but never expose sensitive information in error messages. plugin best practices.
Plugins execute in the security context of the calling user by default. Use impersonation sparingly and only when you need system-level privileges. Always validate and sanitize any data that comes from user input. impersonation in plugins.
Conclusion
Mastering Dynamics 365 plugin development requires deep understanding of the event pipeline, execution context, and platform constraints. By choosing the right stage, mode, and registration options, you can build efficient, maintainable solutions that seamlessly extend Dynamics 365's capabilities. Always prioritize performance, handle errors gracefully, and thoroughly test in isolated environments before deploying to production.