Is there any native way to access Office 365 user calendar and shared calendars?

0
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I am developing an application that normally would read and write all calendars in an Office 365 tenant. This is straightforward with app-permissions. But the client decided not to allow this scenario, neither delegated permissions. They want a solution where there is no any app registration needed in the Azure AD (don't ask me why). They want to share all affected calendars with a dedicated user and I should use non-REST API methods to read and write those shared calendars.

So I am looking for any native way. I am thinking about IMAP, as Outlook is using this protocol to connect. But only knowing the email address, how can I discover the server to connect to?

Supposing I can get that information, or I can somehow avoid relying on this, can anyone suggest me an IMAP library for .NET 4+ (4.6+ preferably) that is capable of handling calendars. Commercially supported(!) library suggestions are also welcome.

(Note: thanks, I can google for myself, I would appreciate the first-hand experience :) )

Thank you.

1
office365imap.net-4.6
Calendars are not an IMAP feature. – Max
Thank you. Then what is Outlook using? – ZorgoZ
Windows outlook: MAPI; Mac Outlook: EWS. – Max
Ok, then Windows Outlook is still getting Calendar with MAPI. Doesn't it? – ZorgoZ
Windows Outlook, in general, uses MAPI for everything. It's the native protocol for it. – Max

1 Answers

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Fortunately, Office365 has Exchange server under the hood, that supports Exchange Web Services. EWS does exactly what I need, although it is a little bit slower.