Mine!

using System;
using System.IO;
using System.Threading;
using System.Diagnostics;

public class Logger {

        private string filename = "logger.log";
        private StreamWriter writer;

        public Logger () {
                if (!File.Exists (filename))
                        writer = new StreamWriter (File.Create (filename));
                else
                        writer = File.AppendText (filename);

                Console.WriteLine ("File opened.");
        }

        public void Close () {
                writer.Close ();
                Console.WriteLine ("File closed");
        }

        static void Main (string [] args) {
                Logger l1 = new Logger ();
                Console.WriteLine ("Hit ^C to abort this application.");
                System.Threading.Thread.Sleep (10000);
        }
}