Access a recurring series by using EWS in Exchange

Learn how to access calendar items in a recurring series by using the EWS Managed API or EWS in Exchange.

A recurring series of appointments or meetings is made up of a recurring master, a number of occurrences in a series that repeat according to a set pattern, and, optionally, sets of occurrences that were changed and that were deleted. You can use the EWS Managed API or EWS to access calendar items in a recurring series. This enables you to:

  • Check to see if a calendar item associated with an item ID is a recurring master, an occurrence in a series, or an exception to a series.

  • Search your calendar folder for recurrence appointments.

  • Get related recurrence calendar items

  • Iterate through occurrences in a series, occurrence exceptions, or occurrence deletions.

Get a collection of recurring calendar items by using the EWS Managed API

If you want to retrieve a collection of appointments, you can use the ExchangeService.FindAppointments method to retrieve all appointments between a given start and end date, and then add all calendar items with an appointment type of Occurrence or Exception to a collection, as shown in the following example.

This example assumes that you have authenticated to an Exchange server and have acquired an ExchangeService object named service.

public static Collection<Appointment> FindRecurringCalendarItems(ExchangeService service, 
                                                                    DateTime startSearchDate, 
                                                                    DateTime endSearchDate)
{
    // Instantiate a collection to hold occurrences and exception calendar items.
    Collection<Appointment> foundAppointments = new Collection<Appointment>();
    // Create a calendar view to search the calendar folder and specify the properties to return.
    CalendarView calView = new CalendarView(startSearchDate, endSearchDate);
    calView.PropertySet = new PropertySet(BasePropertySet.IdOnly, 
                                            AppointmentSchema.Subject, 
                                            AppointmentSchema.Start, 
                                            AppointmentSchema.IsRecurring, 
                                            AppointmentSchema.AppointmentType);
    // Retrieve a collection of calendar items.
    FindItemsResults<Appointment> findResults = service.FindAppointments(WellKnownFolderName.Calendar, calView);
    // Add all calendar items in your view that are occurrences or exceptions to your collection.
    foreach (Appointment appt in findResults.Items)
    {
        if (appt.AppointmentType == AppointmentType.Occurrence || appt.AppointmentType == AppointmentType.Exception)
        {
            foundAppointments.Add(appt);
        }
        else
        {
            Console.WriteLine("Discarding calendar item of type {0}.", appt.AppointmentType);
        }
    }
    return foundAppointments;
}

Note that recurring master calendar items aren't returned in a call to FindAppointments. If you want to retrieve recurring masters, or you want a more general approach to retrieving calendar items, you need to use ExchangeService.FindItems. You can then use a search filter to retrieve only items with a start date greater than or equal to a date you choose, and an item view to limit the number of items to return. Note that a recurring master with a start date earlier than the start date in your search will not be found, even if occurrences occur in this range.

This example assumes that you have authenticated to an Exchange server and have acquired an ExchangeService object named service.

public static Collection<Appointment> FindCalendarItemsByAppointmentType(ExchangeService service, 
                                                                         AppointmentType myAppointmentType, 
                                                                         DateTime startSearchDate)
{
    Collection<Appointment> foundAppointments = new Collection<Appointment>();
    // Create a search filter based on the start search date.
    SearchFilter.SearchFilterCollection searchFilter = new SearchFilter.SearchFilterCollection();
    searchFilter.Add(new SearchFilter.IsGreaterThanOrEqualTo(AppointmentSchema.Start, startSearchDate));
    // Create an item view to specify which properties to return.
    ItemView view = new ItemView(20);
    view.PropertySet = new PropertySet(BasePropertySet.IdOnly, 
                                       AppointmentSchema.Subject, 
                                       AppointmentSchema.Start, 
                                       AppointmentSchema.AppointmentType,
                                       AppointmentSchema.IsRecurring);
    // Get the appointment items from the server with the properties we specified.
    FindItemsResults<Item> findResults = service.FindItems(WellKnownFolderName.Calendar, searchFilter, view);
    // Add each of the appointments of the type you want to the collection.
    foreach (Item item in findResults.Items)
    {
        Appointment appt = item as Appointment;
        if (appt.AppointmentType == myAppointmentType)
        {
            foundAppointments.Add(appt);
        }
    }
    return foundAppointments;
}

Sometimes you have one piece of the puzzle, but to solve it you need the rest of the pieces. If you have the item ID for a recurrence calendar item, you can get the other pieces you need by using one of several EWS Managed API properties or methods.

Table 1. EWS Managed API property or method to use to get related recurrence calendar items

If you have the item ID for… You can get… By using the…
The recurring master calendar item
The first occurrence in a series
The last occurrence in a series
The exceptions to a series
The deleted appointments in a series
Any occurrence (given its index)
Appointment.FirstOccurrence property
Appointment.LastOccurrence property
Appointment.ModifiedOccurrences property
Appointment.DeletedOccurrences property
Appointment.BindToOccurrence method
A single occurrence in a series
The recurring master
Appointment.BindToRecurringMaster method
Any calendar item (an Appointment object)
The appointment type enumeration value
Appointment.AppointmentType property

The following code example shows how to get a recurring master, the first or last occurrence in a series, or an occurrence given its index.

This example assumes that you have authenticated to an Exchange server and have acquired an ExchangeService object named service.

public static void GetRelatedRecurrenceCalendarItems(ExchangeService service, ItemId itemId)
{
    Appointment calendarItem = Appointment.Bind(service, itemId, new PropertySet(AppointmentSchema.AppointmentType));
    Appointment recurrMaster = new Appointment(service);
    PropertySet props = new PropertySet(AppointmentSchema.AppointmentType,
                                        AppointmentSchema.Subject,
                                        AppointmentSchema.FirstOccurrence,
                                        AppointmentSchema.LastOccurrence,
                                        AppointmentSchema.ModifiedOccurrences,
                                        AppointmentSchema.DeletedOccurrences);
    // If the item ID is not for a recurring master, retrieve the recurring master for the series.
    switch (calendarItem.AppointmentType)
    {
        // Calendar item is a recurring master so use Appointment.Bind
        case AppointmentType.RecurringMaster:
            recurrMaster = Appointment.Bind(service, itemId, props);
            break;
        // The calendar item is a single instance meeting, so there are no instances to modify or delete.
        case AppointmentType.Single:
            Console.WriteLine("Item id must reference a calendar item that is part of a recurring series.");
            return;
        // The calendar item is an occurrence in the series, so use BindToRecurringMaster.
        case AppointmentType.Occurrence:
            recurrMaster = Appointment.BindToRecurringMaster(service, itemId, props);
            break;
        // The calendar item is an exception to the series, so use BindToRecurringMaster.                
        case AppointmentType.Exception:
            recurrMaster = Appointment.BindToRecurringMaster(service, itemId, props);
            break;
    }
    // View the first occurrence, last occurrence, and number of modified and deleted occurrences associated with the recurring master.
    Console.WriteLine("Information for the {0} recurring series:", recurrMaster.Subject);
    Console.WriteLine("The start time for the first appointment with id \t{0} was on \t{1}.", 
                        recurrMaster.FirstOccurrence.ItemId.ToString().Substring(144), 
                        recurrMaster.FirstOccurrence.Start.ToString());
    Console.WriteLine("The start time for the last appointment with id \t{0} will be on \t{1}.", 
                        recurrMaster.LastOccurrence.ItemId.ToString().Substring(144), 
                        recurrMaster.LastOccurrence.Start.ToString());
    Console.WriteLine("There are {0} modified occurrences and {1} deleted occurrences.", 
                        recurrMaster.ModifiedOccurrences == null ? "no" : recurrMaster.ModifiedOccurrences.Count.ToString(), 
                        recurrMaster.DeletedOccurrences == null ? "no" : recurrMaster.DeletedOccurrences.Count.ToString());
    // Bind to the first occurrence of a series by using its index.
    Appointment firstOccurrence = Appointment.BindToOccurrence(service, 
                                                                recurrMaster.Id, 
                                                                1, // Index of first item is 1, not 0.
                                                                new PropertySet(AppointmentSchema.AppointmentType,
                                                                                AppointmentSchema.Start));
    Console.WriteLine("Compare the start times for a recurring master's first occurrence " + 
                        "and the occurrence found at index 1 using the BindToOccurrence method:");
    Console.WriteLine("The appointment at index 1 has a start time of\t\t\t\t {0}\n" +
                        "Which matches that of the first occurrence on the recurring master: \t {1}",
                        firstOccurrence.Start.ToString(),
                        recurrMaster.FirstOccurrence.Start.ToString());
}

Access calendar items in a recurring series by using EWS

Accessing calendar items in a recurring series is very similar to accessing single instances of calendar items. You use a GetItem operation request, specifying the properties you want, with the OccurrenceItemId of the appointment instance you need. The OccurrenceItemId contains the ItemID of the occurrence's recurring master, as well as its index value in the series.

The following XML shows the GetItem request used to return an occurrence in a series specified by its index. Note that the ItemID of the recurring master has been shortened for readability.

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
               xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages" 
               xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types" 
               xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Header>
    <t:RequestServerVersion Version="Exchange2010" />
  </soap:Header>
  <soap:Body>
    <m:GetItem>
      <m:ItemShape>
        <t:BaseShape>IdOnly</t:BaseShape>
        <t:AdditionalProperties>
          <t:FieldURI FieldURI="calendar:CalendarItemType" />
          <t:FieldURI FieldURI="calendar:Start" />
        </t:AdditionalProperties>
      </m:ItemShape>
      <m:ItemIds>
        <t:OccurrenceItemId RecurringMasterId="AAMkA" InstanceIndex="1" />
      </m:ItemIds>
    </m:GetItem>
  </soap:Body>
</soap:Envelope>

The server responds to the GetItem request with a GetItemResponse message that includes a ResponseCode value of NoError, which indicates that the email was created successfully, and the ItemId of the newly created message.

See also