internal class MyClass
    {
        private bool _isDone;
        static void Main(string[] args)
        {
            var instance = new MyClass();
            var thread = new Thread(instance.DoWork);
            thread.Start();
            instance.DoWork();
            Console.Read();
        }

        private void DoWork()
        {
            if (!_isDone)
            {
                _isDone = true;
                Console.WriteLine("Work done");
            }
        }
    }