// 客户端调用

    // 类似Web应用程序

    class Client

    {

        static void Main(string[] args)

        {

            BusinessObject customers = new CustomersBusinessObject("ShangHai");

            customers.Dataacces = new CustomersDataAccess();

            customers.Add("小六");

            Console.WriteLine("增加了一位成员的结果：");

            customers.ShowAll();

            customers.Delete("王五");

            Console.WriteLine("删除了一位成员的结果：");

            customers.ShowAll();

            Console.WriteLine("更新了一位成员的结果：");

            customers.Update("Learning_Hard");

            customers.ShowAll();

            Console.Read();

        }

    }

    // BLL 层

    public class BusinessObject

    {

        // 字段

        private DataAccess dataacess;

        private string city;

        public BusinessObject(string city)

        {

            this.city = city;

        }

        // 属性

        public DataAccess Dataacces

        {

            get { return dataacess; }

            set { dataacess = value; }

        }

        // 方法

        public virtual void Add(string name)

        {

            Dataacces.AddRecord(name);

        }

        public virtual void Delete(string name)

        {

            Dataacces.DeleteRecord(name);

        }

        public virtual void Update(string name)

        {

            Dataacces.UpdateRecord(name);

        }

        public virtual string Get(int index)

        {

            return Dataacces.GetRecord(index);

        }

        public virtual void ShowAll()

        {

            Console.WriteLine();

            Console.WriteLine("{0}的顾客有：", city);

            Dataacces.ShowAllRecords();

        }

    }

    public class CustomersBusinessObject : BusinessObject

    {

        public CustomersBusinessObject(string city)

            : base(city) { }

        // 重写方法

        public override void ShowAll()

        {

            Console.WriteLine("------------------------");

            base.ShowAll();

            Console.WriteLine("------------------------");

        }

    }

    /// <summary>

    /// 相当于三层架构中数据访问层（DAL）

    /// </summary>

    public abstract class DataAccess

    {

        // 对记录的增删改查操作

        public abstract void AddRecord(string name);

        public abstract void DeleteRecord(string name);

        public abstract void UpdateRecord(string name);

        public abstract string GetRecord(int index);

        public abstract void ShowAllRecords();

    }

    public class CustomersDataAccess:DataAccess

    {

        // 字段

        private List<string> customers =new List<string>();

        public CustomersDataAccess()

        {

            // 实际业务中从数据库中读取数据再填充列表

            customers.Add("Learning Hard");

            customers.Add("张三");

            customers.Add("李四");

            customers.Add("王五");

        }

        // 重写方法

        public override void AddRecord(string name)

        {

            customers.Add(name);

        }

        public override void DeleteRecord(string name)

        {

            customers.Remove(name);

        }

        public override void UpdateRecord(string updatename)

        {

            customers[] = updatename;

        }

        public override string GetRecord(int index)

        {

            return customers[index];

        }

        public override void ShowAllRecords()

        {

            foreach (string name in customers)

            {

                Console.WriteLine(" " + name);

            }

        }

    }