I want get Caller's Caller Id information, when state of phone is Ringing

If you want your app to be notified when there is an incoming call: https://developer.ringcentral.com/api-docs/latest/index.html#!#RefGetDetailedExtensionPresenceEvent

https://github.com/ringcentral/ringcentral-csharp-client#subscription

Then you can fetch the active calls to get detailed information: https://developer.ringcentral.com/api-docs/latest/index.html#!#RefExtensionActiveCalls.html

Thanks your reply.
your message has helped me.
I have one more question.
After the call is completed, i am going to download recorded wav file.
as phone's state become to "NoCall" form "CallConnected", I am going to download recorded wav file.  But at this time recorded wav file isn't generated yet.
when should i download file.
I'd like to get notification about generation of wav file.
Is this possible?.
can I use function of subscription?
I believe you will help me.
kind regard.

I am not aware of a notification for wav file generation. I am afraid that you have to do a poll in a short period of time to check the existence of call recording.