With Exchange Web Services a calendar event can be created and assigned to a specific category while that same capability is missing from Graph - microsoft-graph-api

Question

I have been using EWS to create appointments in both Exchange on-premise and Exchange online mailboxes that include a category value. I'm trying to migrate to Microsoft Graph since it's the recommended path according to Microsoft https://learn.microsoft.com/en-us/graph/migrate-exchange-web-services-overview
One of the EWS capabilities I can't replicate is creating a calendar event with a category.
The EWS Appointment class supports setting the category for the appointment - https://learn.microsoft.com/en-us/dotnet/api/microsoft.exchange.webservices.data.appointment?view=exchange-ews-api
When testing with Graph to create a calendar event, all responses to the posted requests include a null categories array as shown in the documentation - https://learn.microsoft.com/en-us/graph/api/user-post-events?view=graph-rest-1.0&tabs=csharp so it would seem that a request can be made with category.
Using the Microsoft Graph explorer to create a calendar event I naively add the categories property as an array and include a known category from the user's mailbox:
{
"subject": "Test",
"isAllDay": true,
"ShowAs":"Free",
"categories": [
{ "displayName":"Red Category", "color": "preset0" },
],
"start": {
"dateTime": "2022-11-08T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
},
"end": {
"dateTime": "2022-11-09T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
}
}
The response is always:
{
"error": {
"code": "UnableToDeserializePostBody",
"message": "were unable to deserialize "
}
}
I have also changed the property to a key:value which gets the same reponse.
{
"subject": "Test",
"isAllDay": true,
"ShowAs":"Free",
"category": "Red Category",
"start": {
"dateTime": "2022-11-08T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
},
"end": {
"dateTime": "2022-11-09T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
}
}
Does the Graph Create Event POST /users/{id | userPrincipalName}/calendars/{id}/events support including a category?

Answer 1

You were so close.
Categories is an array of strings. This will create the appointment with the Personal category, if there is no Personal category one will be created.
{
"subject": "Test",
"isAllDay": true,
"ShowAs": "Free",
"categories": [
"Personal"
],
"start": {
"dateTime": "2022-11-08T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
},
"end": {
"dateTime": "2022-11-09T00:00:00.0000000",
"timeZone": "Eastern Standard Time"
}
}