The c# quickstart const for RINGCENTRAL_PRODUCTION is not explained.

Are you talking about this link?

https://github.com/ringcentral/ringcentral-api-docs/blob/master/docs/call-management/quick-start/c-sharp.md

Most probably the constant

RINGCENTRAL_PRODUCTION

will be the true for production

Thanks for pointing out the missing param! It is just true or false for production environment or sandbox environment, respectively. I will update the dev guide asap.