Recently I had to integrate a Node.js based server application with a C# DLL. Our software (a web-app) offers the possibility to execute payments over a POS terminal. This latter one is controllable through a dedicated DLL which exposes interfaces like ExecutePayment(operation, amount) and so on. As I mentioned, there is the Node.js server that somehow exposes the functionality of the POS (and some more) as a REST api. (The choice for using Node.js had specific reasons which I wouldn't want to outline right now).