C#中is与As运算符号的使用详解

如下所示：

using system;
using system.collections.generic;
using system.text;
namespace consoleapplication1
{
    class isorasclass
    {
        class animal
        {
            public void eat()
            {
                console.writeline("eating...");
            }
            public override string tostring()
            {
               return  "i am eating";
            }
        }
        //家禽类
        class jia:animal
        {

        }
        //狗
        class dog : jia
        {

        }
        //鸟
        class bird
        {

        }
        static void main()
        {
           isorasclass app=new isorasclass();
           //
           dog d=new dog();
           app.useisopreate(d);
           app.useasopreate(d);
           //
           bird b = new bird();
           app.useasopreate(b);

        }
        //使用is运算符
        void useisopreate(animal a)
        {
            if (a is jia)
            {
                jia j = (jia)a;
                j.eat();
            }
        }
        //使用as运算符
        void useasopreate(object o)
        {
            jia j = o as jia;
            if (j != null)
            {
                console.writeline(j.tostring());
            }
            else
            {
                console.writeline("{0} is not animal", o.gettype().name);
            }
        }
    }
}