Delta query + odata.maxpagesize on calendarView/delta returns more items than requested when a recurring master expands; odata.nextLink results in infinite pagination loop

[DasekaX]

Describe the bug

We are encountering 2 issues when retrieving Events with GetAsDeltaGetResponseAsync and using a maxpagesize header.

1. When a recurring master event has a recurrence pattern that expands into more individual occurrences than the configured odata.maxpagesize, the server returns more items than the requested page size.

2. The @odata.nextLink returned points to a next page that, when fetched, contains duplicates of events already received. That next page in turn contains a nextLink which returns the same events again, producing an endless loop.

If maxpagesize is larger than the returned events for a master event including the individual occurrences, then there is no issue

Expected behavior

• The returned events should be less or equal to odata.maxpagesize
• @odata.nextLink must point to a subsequent page that contains only new, non-duplicated items. Pagination tokens should not cause previously-returned items to reappear.

How to reproduce

1. Create or identify a recurring master event whose recurrence rule expands to more than the intended page size within your query time window (for example a yearly/daily rule with many occurrences).
2. Request /users/{id}/calendarView/delta with StartDateTime, EndDateTime and header Prefer: odata.maxpagesize={N}.
3. Inspect the first response:

• Count of returned items can be > N.
• A @odata.nextLink is present.

4. GET the @odata.nextLink:

• Response contains items that were already included in the previous page (duplicates).
• A new @odata.nextLink is present and steps 3–4 repeat → infinite loop.

SDK Version

5.103.0

Latest version known to work for scenario above?

No response

Known Workarounds

No response

Debug output

Click to expand log

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### Configuration

_No response_

### Other information

_No response_

[jbennink]

This is also happening to me. At the moment it is only happening for a calendar that is being synced the first time, so I'm calling something like this

                    return _exchangeService.Users[_userMailbox].CalendarView
                       .Delta.GetAsDeltaGetResponseAsync(config =>
                       {
                           config.QueryParameters.StartDateTime = DateTime.UtcNow.AddMonths(-1).ToString("yyyy-MM-dd");
                           config.QueryParameters.EndDateTime = DateTime.UtcNow.AddYears(10).ToString("yyyy-MM-dd");
                       })

It gets stuck in an infite loop and this set also has 3 recurring appointments. Other calendars that already have a deltatoken don't seem affected (or perhaps there are no recurring appointmsn (new of changed).

Since it is occuring on prduction code on an older version of the library and in development with the most recent libraries it feels like Microsoft broke something on their back-end.

[jbennink]

So I also found this on learn.microsoft.com: https://learn.microsoft.com/en-us/answers/questions/5790953/graph-api-calendar-events-delta-query-infinite-loo?source=docs

Based on that feedback (and another github post that I don't have handy now I also experimented with changes the maxpagesize. In my case I first set it to 25 fixed. This was still strange since the first batch had 25, the second link got me another 25, the third call gave me 36 and then a call gave met 523. After that I got 0 new items and a delta link instead of a nextlink.

I guess the prefer is counting appointment (events) but recurring instances of the event are not counted and added. I think the 36 and the 523 contained the recurring versions of 3 events that I know were recurring in this calendar.

This was the first sync, which Is why my first call was wit hthe code I posted 3 days before, using StartDateTime and EndDateTime. Now I will be in the loop using the Delta token like so:

                // Return changes after the last sync
                return _exchangeService.Users[_userMailbox].CalendarView
                    .WithUrl(deltaLink)
                    .Delta
                    .GetAsDeltaGetResponseAsync(config =>
                    {
                        config.Headers.Add("Prefer", "odata.maxpagesize=25");
                    })

The header is just hacked in for now until I can tidy things up or MS fixes this bug.