PlatformDetector.cs

using System;
 
class Program {
 
        static void Main ()
        {
                int p = (int) Environment.OSVersion.Platform;
                if ((p == 4) || (p == 6) || (p == 128)) {
                        Console.WriteLine ("Running on Unix");
                } else {
                        Console.WriteLine ("NOT running on Unix");
                }
        }
}