老鹰eagle、麻雀sparrow、鸵鸟ostrich都是鸟类birds，根据三者的共性，提取出鸟类作为父类；并且各自具有格子的特点，老鹰吃小鸡，麻雀吃粮食，鸵鸟吃青草。

class ostrich:bird
    {
        public override void Write()
        {
            Console.WriteLine("鸵鸟吃青草");
        }
    }

class sprraw:bird
    {
        public override void Write()
        {
            Console.WriteLine("麻雀吃粮食");
        }
    }

class eagle:bird
    {
        public override void Write()
        {
            Console.WriteLine("老鹰吃小鸡");
        }
    }

abstract class bird
    {
        public abstract void Write();

    }

class Program
    {
        static void Main(string[] args)
        {
            bird myEagle = new eagle();
            bird mySparrow = new sprraw();
            bird myOstrich = new ostrich();
            bird[] myBird = { myEagle,mySparrow,myOstrich};
            foreach (bird outBird in myBird) outBird.Write();
            Console.ReadKey();
        }