Mapping error in Nhibernate

 class Employee
    {
        public int id;
        public string name;

        public int getID
        {
            get
            {
                return id;
            }
            set
            {
                id = value;
            }
        }
        public string SayHello()
        {

         return string.Format("'Hello World!', said {0}.", name);

        }
        public string getName
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
            }
        }



    }

 static void Main(string[] args)
        {
            //Employee fred = new Employee();
            //fred.name = "Tran Tuan Van";

            //Console.WriteLine(fred.SayHello());

            CreateEmployeeAndSaveToDatabase();
           // UpdateTobinAndAssignPierreHenriAsManager();
           // LoadEmployeesFromDatabase();
            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();

            Console.ReadKey();
        }
        static void CreateEmployeeAndSaveToDatabase()
        {
            Employee tobin = new Employee();
            tobin.name = "Tobin Harris";
            tobin.id = 1;

            using (ISession session = OpenSession())
            {
                try
                {
                    using (ITransaction transaction = session.BeginTransaction())
                    {
                        session.Save(tobin);
                        transaction.Commit();
                    }
                }
                catch (Exception ex)
                {
               
                  
                }
                Console.WriteLine("Saved Tobin to the database");
            }
        }