C# 中的接口

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

namespace Wrox.ProeCSharp
{
    interface IBankAccount
    {
        void PayIn(decimal account);      //方法不用实现，类继承是重写  
        bool WithDraw(decimal account);  //方法不用实现，类继承是重写  
        decimal Balance { get; }    //注意是属性，不是字段

    }
}

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


namespace Wrox.ProeCSharp.VenusBank
{
    class VenusAccount : IBankAccount
    {
        public decimal balance;
        public void PayIn(decimal account)
        {
            balance += account;
        }

        public  bool WithDraw(decimal account)
        {
            if (balance >= account)
            {
                balance -= account;
                return true;
            }
            Console.WriteLine("WithDraw  fail!");
            return false;
        }
        public decimal Balance
        {
            get { return balance; }
        }
        public override string ToString()
        {
            return string.Format("Venus bank saver: Balance= {0,6:C}", balance);
        }

    }
}

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

namespace Wrox.ProeCSharp.JupiteBank
{
    class JupiteAccount:IBankAccount
    {
        public decimal balance;
        public void PayIn(decimal account)
        {
            balance += account;
        }

        public bool WithDraw(decimal account)
        {
            if (balance >= account)
            {
                balance -= account;
                return true;
            }
            Console.WriteLine("WithDraw  fail!");
            return false;
        }
        public decimal Balance
        {
            get { return balance; }
        }

        public override string ToString()
        {
            return string.Format("Gold bank saver: Balance= {0,6:C}", balance);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Wrox.ProeCSharp.JupiteBank;
using Wrox.ProeCSharp.VenusBank;
namespace Wrox.ProeCSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            VenusAccount venus = new VenusAccount();
            JupiteAccount jupite = new JupiteAccount();

            venus.PayIn(200);
            venus.WithDraw(300);
            Console.WriteLine(venus.ToString());

            jupite.PayIn(600);
            jupite.WithDraw(500);
            jupite.WithDraw(100);
            Console.WriteLine(jupite.ToString());

            Console.ReadLine();

        }
    }
}