How to detect if an appointment in OnAppointmentSend event is a canceled meeting in Outlook Add-in?

Question

We have an Outlook add-in that uses the OnAppointmentSend launch event. It works correctly for normal meeting sends, but we need to detect when the user is sending a cancellation for an existing meeting.

Is there a way to determine from the event payload whether the appointment received by the OnAppointmentSend event is a cancellation rather than a new or updated meeting?

For example, is there a specific property or flag available in the event object that indicates the meeting is being canceled?

Any guidance or documentation references would be appreciated.

Answer 1

To detect if an appointment in the OnAppointmentSend event is a cancellation in your Outlook add-in, you can utilize the MeetingRequest.IsCancelled property from the Exchange Web Services (EWS) API. This property indicates whether the appointment has been canceled.

Here’s how you can check for a cancellation:

1. When handling the OnAppointmentSend event, you can retrieve the appointment details using the EWS API.
2. Check the IsCancelled property of the MeetingRequest object. If it returns true, then the appointment is a cancellation.

This approach allows you to differentiate between a new meeting, an updated meeting, and a cancellation based on the state of the appointment when the event is triggered.

For more detailed information, you can refer to the EWS API documentation regarding the MeetingRequest.IsCancelled property.

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References:

• MeetingRequest.IsCancelled Property

Answer 2

Hi @Vinod Bhatt 

Thank you for posting your question in the Microsoft Q&A forum. 

Currently, Outlook does not expose any supported property or flag in the OnAppointmentSend event payload that can reliably indicate when the user is sending a cancellation instead of a new or updated meeting. As a result, add‑ins cannot programmatically differentiate cancellations using the event object alone.

This issue has been discussed by multiple developers, and you can find a related discussion here: "Send Cancellation" triggers OnAppointmentSend launch event in Classic Outlook and not on New or We… 

We completely understand how important this functionality is for your scenarios. To help guide future improvements, we encourage you to share your experience through the Ideas · Community. When submitting, you can also attach the link to this thread so others facing the same challenge can upvote it. This helps bring visibility to Microsoft engineering. 

We greatly value your input. By sharing your experience, you help shape the product in ways that benefit the entire community. Thank you for contributing and supporting the ongoing improvement of our product. 

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