class Program
    {
        static void Main(string[] args)
        {
            Test1 t = new Test2();
            Console.Write(t.GetString());
            Console.Read();
        }
    }
    class Test1
    {

        public virtual string GetString()
        {
            return "1";
        }
    }
    class Test2 : Test1
    {
        public override string GetString()
        {
            return "2";
        }

    }