I used C# Graph SDK(Microsoft.Graph 5.61.0) to test Patch an Event with Application Permission

/*Calendars.ReadWrite | Application | Read and write calendars in all mailboxes | Yes*/
var client = GetAppGraphServiceClient(config);
if (client == null) {
    Console.WriteLine("Init Graph Client Error...");
    return;
}

string userId = "user-id";
string eventId = "event-id";
var theEvent = await client.Users[userId].Events[eventId].GetAsync();

var updatedAttendees = new List<Attendee>();
theEvent.Attendees.ForEach(attendee =>
{
    if (attendee.EmailAddress.Address != "[email protected]")
    {
        //Attendee attendee1 = new Attendee();
        //EmailAddress emailAddress1 = new EmailAddress();
        //emailAddress1.Address = attendee.EmailAddress.Address;
        //attendee1.EmailAddress = emailAddress1;
        //updatedAttendees.Add(attendee1);

        updatedAttendees.Add(attendee);
    }
});

var updatedEvent = new Event
{
    Attendees = updatedAttendees
};

var newEvent = await client.Users[userId].Events[eventId].PatchAsync(updatedEvent);

//@event.Attendees = updatedAttendees;
//var updated = await client.Users[userId].Events[eventId].PatchAsync(@event);

but the Attendees of newEvent have no any change compared with theEvent whether it is a one-time removal or one-by-one removal.

I try to change Subject and it effects

var updatedEvent2 = new Event
{
    Subject = "Updated Subject",
};

var newEvent2 = await client.Users[userId].Events[eventId].PatchAsync(updatedEvent2);
//it had is changed

I also tested patching OnlineMeeting with an application permission and application access policy. I added two attendees as participants, then tried to remove the two attendees one at a time. However, the attendees list didn’t change. If I just try to remove first attendee, it succeeded, afterwards there was just one attendee in the meeting. If I then tried to remove last attendee, the attendees list didn’t change at all.

var theMeeting = await client.Users[userId].OnlineMeetings[onlineMeetingId].GetAsync();

var updatedMeeting = new OnlineMeeting
{
    Participants = new MeetingParticipants
    {
        Attendees = new List<MeetingParticipantInfo>(),
    }
};

var newMeeting = await client.Users[userId].OnlineMeetings[onlineMeetingId].PatchAsync(updatedMeeting);

How can I use PATCH Attendees to correctly remove attendees?