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Is there a example to achieve this through asp.net

This is largely going to depend upon "when" you need the data, but to broadly answer your question, you can use either the active-calls or presence for a particular extension.

If you need the data in near-real-time, I would recommend creating a Subscription (Push Notification) or Webhook (also Push Notification) for the Extension(s) you wish to receive this information. Here is a sample application showing how to use RingCentral Subscriptions. Here is a sample application showing how to use RingCentral Webhooks. Here is the documentation for Push Notifications.

If you need the incoming caller's phone number you can also use the active-calls or presence as I listed initially, but the rate limiting on these may restrict your usage of these resources which is why I suggested Subscriptions or Webhooks.

If you need this for analysis, I would recommend using Call-Log, and set the query parameter 'view=Detailed'.