I am trying to retrieve custom property value for an event using Outlook REST API (version 2.0). The custom property was created by an Outlook Office.js Add-ins.
Here is request:
/v2.0/me/calendar/?$expand=singleValueExtendedProperties($filter=PropertyId eq 'Binary 0x0FFF')
This returns a successful response from API but it does not return the singleValueExtendedProperty.
To get custom property, you would require an (REST) item identifier and custom properties are only applicable on messages and events.
Below are the templates for message and event respectively.
/me/messages/'<ITEM_ID>'?$expand=SingleValueExtendedProperties($filter=PropertyId eq 'String {00020329-0000-0000-c000-000000000046} Name cecp-<ADD_IN_GUID>')
/me/events/<ITEM_ID>'?$expand=SingleValueExtendedProperties($filter=PropertyId eq 'String {00020329-0000-0000-c000-000000000046} Name cecp-<ADD_IN_GUID>')
