Get outlook recurrence pattern of a event in iCal format using C#

I am developing a system which extract the outlook calendar data and save it on android device calendar. Up to now all other outlook data are extracted and saved successfully. Now I need to create recurrence rule (rrule). Because android device calendar use to save recurrence pattern as a rule which is mentioned as rfc5545 standard. So how can I extract outlook recurrence pattern as a rule (like iCal format).

In briefly, I need to get recurrence pattern of the Outlook calendar event as like this

RRULE:FREQ=DAILY;UNTIL=20000131T140000Z;BYMONTH=1

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you need to use the Office RecurrencePattern Object see msft docs which represents the pattern of incidence of recurring appointments for the associated AppointmentItem object.

the object has RecurrenceType (olRecursDaily, olRecursMonthly, ...) which have themselves properties (Interval, DayOfWeekMask, DayOfMonth, ...)

with this information you can build the string defined by rfc5545.

one example implementation is available see : sourceforge otlook2ical