We have a RingCentral C# SDK available:
https://github.com/ringcentral/ringcentral-csharpIt shows usage as something like this (I am not a C# developer, so my code example below may not be correct, and I would recommend you ask any questions you have about using this SDK in the Github Issues for the repository:
//import RingCentral
using RingCentral; //Initialize Ring Central Client var sdk = new SDK( "your appKey", "your appSecret", "RingCentral apiServer", "Application Name", "Application Version"); var authResponse = sdk.Platform.Login(userName, extension, password, true); var ringoutPostBodyJson = "{\"from\":{\"phoneNumber\":\"\",\"forwardingNumberId\":\"\"},\"to\":{\"phoneNumber\":\"\"},\"callerId\":{\"phoneNumber\":\"\"},\"playPrompt\":false,\"country\":{\"id\":\"\"}}";
var request = new Request("/restapi/v1.0/account/~/extension/~/ringout", ringoutPostBodyJson);
var ringoutResponse = sdk.Platform.Post(request);