MB-230 Extend Customer Service Practice Question
You are extending a Customer Service environment by creating a custom action that will be triggered from a case record. The action must call an external REST API, pass the case ID, and update the case with the response. You have written a plug-in that implements the logic. Where should you register the plug-in step to ensure it executes when the custom action is invoked?
⚠ Common exam trap
It's easy for candidates to confuse custom action messages with standard entity messages, leading to registration on Create or Update instead of the custom action itself.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
On the custom action message, post-operation.
To have a plug-in execute when a custom action is invoked, you must register a step on that custom action's message. Post-operation is appropriate because it runs after the action's main logic, allowing access to output parameters and the ability to update the case. Registering on entity messages like Create, Update, or Retrieve would trigger at incorrect times and not align with the action invocation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
On the Retrieve message of the Case entity, post-operation.
Why it's wrong here
The Retrieve message occurs when a case is read, not when a custom action is invoked. Registering here would cause the plug-in to run on every retrieval, which is inefficient and unrelated to the action's trigger. It would not receive the custom action's input parameters. This approach fails to connect the plug-in to the custom action execution.
- ✗
On the Update message of the Case entity, pre-operation.
Why it's wrong here
Registering on the Update message would trigger the plug-in whenever any case is updated, not specifically when the custom action is called. This could lead to unintended executions and performance issues. It also does not guarantee that the case ID is available in the same context as the custom action. The custom action message is the correct target for on-demand logic.
- ✗
On the Create message of the Case entity, post-operation.
Why it's wrong here
Registering on the Create message would trigger the plug-in whenever a case is created, not when the custom action is invoked. This would cause the external API call to run at the wrong time, potentially before the case is fully configured or when the case is created through other processes. It does not meet the requirement of executing on demand from the custom action. The correct registration is on the custom action's message.
- ✓
On the custom action message, post-operation.
Why this is correct
Custom actions in Dynamics 365 are exposed as messages. To execute a plug-in when a custom action is invoked, you register a step on that custom action's message. Post-operation ensures the plug-in runs after the action's core logic, allowing you to use the action's output parameters and perform additional updates. This is the standard pattern for extending custom actions with plug-ins.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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