Our Subscription (Push Notification) API resource empowers developers to enable their client application(s) to create a single subscription (to one or more extension's) and continually receive push notifications in real time for each subscribed extension.
However, this subscription has an expiration time but using the official RingCentral SDKs enables developers to automatically renew the subscription(s) on a timely basis.
When using this approach for your application(s) to receive events on your RingCentral account, no polling is involved.
Subscription API: https://developer.ringcentral.com/api-docs/latest/index.html#!#Notifications.htmlView the (official and community developed) RingCentral SDKs:
https://developers.ringcentral.com/library/sdks.html
This question would be best asked in the Github Issue Tracker for the C# SDK Repository, here:
https://github.com/ringcentral/ringcentral-csharp/issues
