#PowerPlatformTip 102: 'Event Coordination'

TL;DR: Use the Microsoft Graph Update Event call with hideAttendees: true to add event attendees silently and keep the guest list private.

💡 Challenge

When you manage event attendees from Power Automate, the standard approach notifies everyone on every change, and by default all attendees can see the full guest list. That’s noisy and, for sensitive events, a privacy problem.

✅ Solution

Update the event directly through the Microsoft Graph API. Setting the event’s hideAttendees property to true keeps the guest list private, and writing the merged attendees array via a PATCH lets you add people without the usual notification flood.

🔧 How It’s Done

1. Get the current event and its attendees.

🔸 GET /events/{event-id} via the Graph API.

🔸 Capture the attendees array from the JSON response.

2. Build the new attendee object(s).

🔸 Each needs an emailAddress (with address and name) and a type (e.g. required).

3. Merge existing and new attendees without duplicates.

🔸 union(existingAttendees, newAttendees).

4. Write the updated list back to the event.

🔸 PATCH /events/{event-id} with the merged attendees array.

🔸 Set "hideAttendees": true in the request body.

5. Optional: grab the full sample flow from GitHub.

🔸 EventCoordination.json

🎉 Result

Attendees are added or updated quietly, keeping notification noise to a minimum, and the guest list stays private, participants only see their own RSVP.

🌟 Key Advantages

🔸 Privacy: the guest list stays hidden, so attendees can’t see each other.

🔸 Notification control: silent updates instead of an alert flood.

🔸 Flexible: add one guest or many with the same call.

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🎥 Video Tutorial

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🛠️ FAQ

1. How do I authenticate the Graph API request? Register a Microsoft Entra ID app, grant it the Calendars.ReadWrite permission, then use Power Automate’s HTTP with Microsoft Entra ID connector to obtain a token and call Graph.

2. What does hideAttendees = true do? It hides the full guest list so attendees only see their own RSVP and cannot view other participants.

3. Can I remove attendees silently as well? Yes. Retrieve the current attendees array, filter out the one you want to remove, then PATCH the event with the updated array and hideAttendees set to true.

🔗 Related Tips

🔸 #PowerPlatformTip 58: ‘HTTP Actions’ - the general-purpose HTTP setup this Graph PATCH call builds on.

🔸 #PowerPlatformTip 138: ‘Graph API via HTTP with Microsoft Entra ID’ - call Graph through a preauthorized connector instead of registering your own Entra ID app.

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