Using C# to host and communicate with node.js This proof of concept launches node.exe as a separate process, redirecting stdin/stdout. It simply calculates 2+2, then sends a process.exit() call after 10 seconds so the (.Net) app can complete (the suppressOut just gets node to output "undefined" instead of the full return value of setTimeout). Da…

NodeFromCSharp.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var proc = new System.Diagnostics.Process();
            proc.StartInfo.CreateNoWindow = true;
            proc.StartInfo.RedirectStandardInput = true;
            proc.StartInfo.RedirectStandardOutput = true;
            proc.StartInfo.UseShellExecute = false;
            proc.StartInfo.RedirectStandardError = true;
            proc.StartInfo.FileName = "node.exe";
            proc.StartInfo.Arguments = "-i";
            proc.Start();
            proc.BeginOutputReadLine();

            proc.StandardInput.WriteLine("2 + 2;");
            proc.StandardInput.WriteLine("setTimeout(function(){ process.exit();}, 10000).suppressOut;");
            proc.OutputDataReceived += proc_OutputDataReceived;
            proc.WaitForExit();
        }

        static void proc_OutputDataReceived(object sender, System.Diagnostics.DataReceivedEventArgs e)
        {
            Console.WriteLine(e.Data);
        }
    }
}

We've built an open source library that does this, Jering.Javascript.NodeJS:

string javascriptModule = @"
module.exports = (callback, x, y) => {  // Module must export a function that takes a callback as its first parameter
    var result = x + y; // Your javascript logic
    callback(null /* If an error occurred, provide an error object or message */, result); // Call the callback when you're done.
}";

// Invoke javascript
int result = await StaticNodeJSService.InvokeFromStringAsync<int>(javascriptModule, args: new object[] { 3, 5 });

// result == 8
Assert.Equal(8, result);

It keeps a Node.js process alive, allowing you to invoke javascript multiple times without starting lots of processes.

Same way running Python code