40 向下转换 as 定义接口

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 向下转换
{
    class Program
    {
        //基类向派生类转换成为向下转换
        //用is关键字进行检查,
        //向下转换如想使用派生类的方法需要进行强制转换
        static void Main(string[] args)
        {
            B b = new B();
            A a = b;
           // a.WordB();//此处报错
            a.Word1();
            if (a is B)
            {
                B b1 = (B)a;
                b1.WordB();
            }
           
        }
    }
    class A
    {
        public void WordA()
        {
            Console.WriteLine("A1");
        }
        public virtual void Word1()
        {
            Console.WriteLine("A");
        }
    }
    class B:A
    {
        public void WordB()
        {
            Console.WriteLine("B1");
        }
        public override void Word1()
        {
            Console.WriteLine("B1");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 向下转换
{
    class Program
    {
        //基类向派生类转换成为向下转换
        //用is关键字进行检查,
        //向下转换如想使用派生类的方法需要进行强制转换
        static void Main(string[] args)
        {
            B b = new B();
            A a = b;
           // a.WordB();//此处报错
            a.Word1();
            if (a is B)
            {
                B b1 = (B)a;
                b1.WordB();
            }
           
        }
    }
    class A
    {
        public void WordA()
        {
            Console.WriteLine("A1");
        }
        public virtual void Word1()
        {
            Console.WriteLine("A");
        }
    }
    class B:A
    {
        public void WordB()
        {
            Console.WriteLine("B1");
        }
        public override void Word1()
        {
            Console.WriteLine("B1");
        }
    }
}

接口：用关键字，interface声明 接口的方法和属性不用加public即使加也会报错。

接口的引用符可以指向多个对象这样就实现了接口的多态。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 接口
{
    class Program
    {
        static void Main(string[] args)
        {
            IBankAccount account = new Bank();
            account.cunkuan(1000);
            account.qukuan(500);
            Console.WriteLine("余额为{0}",account.Blance);
        }
    }
    class Bank:IBankAccount
    {
        private decimal blance;
        public decimal Blance
        {
            get
            {
                return blance;
            }
        }
        public void cunkuan(decimal amount)
        {
            blance += amount;
        }
        public bool qukuan(decimal amount)
        {
            if (blance >= amount)
            {
                blance -= amount;
                return true;
            }
            else
            {
                Console.WriteLine("余额不足，取款失败");
                return false;
            }
        }

}
}