委托的使用 举例猫叫，老鼠逃跑，主人惊醒

  this:指当前类，this调用当前类的属性，方法，包括构造函数的方法，继承本类的构造函数。

base:指当前类的父类，可调用父类的非私有属性，方法，继承父类的构造函数括号里的参数

 一:this 的用处

    1：限定被相识的名称隐藏的成员，方法或函数（多用在构造函数中）

    

 class Person
{
  pricate string name;
  public Person(string name)
 {
   this.name= name;
  }
}

由于this.name 中的name和入参name的名称一样，即被入参隐藏了，所以要用this 限定name是本类的属性

 2：将自己this对象作为参数传递给其他方法

class Teacher  
{  
    public void tshow()  
    {  
        Console.WriteLine("我是老师！");  
        Console.WriteLine(this);//显示的是本类的类名  
    }  
}  

3：声明索引器

private int _index;  
 public int this[int index]  
 {  
     get { return _index; }  
     set { _index = index; }  
 }  

二：base的用处（base实现了多态）

1.在子类中通过base调用父类的构造函数，即在子类初始化时和父类进行通信

    class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person("小李");
            p.show();
            Teacher t = new Teacher("小刘",18);
            t.tshow();
           
            Console.Read();
        }
    }
    class Person
    {
        protected string name;
        public Person(string name)
        {
            this.name = name;
        }
        public void show()
        {
            Console.WriteLine("我属于人类！");
        }
    }
    class Teacher:Person
    {
        
        public Teacher(string name,int age)
            : base(name)
        {
            this.Age = age;
        }
        private int _age;
        public int Age
        {
            get { return _age; }   //读
            set { _age = value; }  //写
        }
        public void tshow()
        {
            Console.WriteLine("我是学生{0}{1}！",name,Age);        
        }      
    }

2.调用基类上已被其它方法重写的方法

    class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person();
            p.show();
            Teacher t = new Teacher();
            t.show();
            Console.Read();
        }
    }
    class Person
    {
        public virtual void show()
        {
            Console.WriteLine("我属于人类");
        }
    }
    class Teacher:Person
    {
        public override void show()
        {
            base.show();
            Console.WriteLine("我是老师");
        }
    }

3.调用基类的构造函数

    class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person();
            p.show();
            Teacher t = new Teacher();
            t.tshow();
            Console.Read();
        }
    }
    
    class Person
    {
        public void show()
        {
            Console.WriteLine("我属于人类");
        }
    }
    class Teacher:Person
    {
        public void tshow()
        {
            base.show();
            Console.WriteLine("我是老师");
        }
    }

在多层继承中：

1>有重载，base指向直接继承的父类

2>无重载，base可指向任意上级父类

 总结

       不能在静态方法中引用this和base，因为当类第一次被加载的时候，静态成员已经被加载到静态存储区，此时类的对象还有可能没有创建，而this和base访问的都是类的实例，也就是对象，而静态成员只能由类访问，不能由对象访问，所以静态方法中不能调用类成员字段

猫叫，老鼠逃跑，主人惊醒的实现方式

public delegate void SubEventHandler();
     public abstract class Subject
     {
         public event SubEventHandler SubEvent;
         protected void FireAway()
         {
             if (this.SubEvent != null)
                 this.SubEvent();
         }   
     }
     public class Cat : Subject
     {  
         public void Cry()
         {
             Console.WriteLine("cat cryed.");
             this.FireAway();
         }
     }
     public abstract class Observer
     {
         public Observer(Subject sub)
         {
             sub.SubEvent += new SubEventHandler(Response);
         }
         public abstract void Response();    
     }
     public class Mouse : Observer
     {
         private string name;
         public Mouse(string name, Subject sub) : base(sub)
         {   
             this.name = name;
         }
         public override void Response()
         {
             Console.WriteLine(name + " attempt to escape!");
         }
     }
     public class Master : Observer
     {
         public Master(Subject sub) : base(sub){}
         public override void Response()
         {
             Console.WriteLine("host waken");
         }
     }
     class Program
     {
         static void Main(string[] args)
         {
             Cat cat = new Cat();
             Mouse mouse1 = new Mouse("mouse1", cat);
             Mouse mouse2 = new Mouse("mouse2", cat);
             Master master = new Master(cat);
             cat.Cry();
         }
 
     }

public interface Observer
     {
         void Response();    //观察者的响应，如是老鼠见到猫的反映
     }
     public interface Subject
     {
         void AimAt(Observer obs);  //针对哪些观察者，这里指猫的要扑捉的对象---老鼠
     }
     public class Mouse : Observer
     {public Mouse(Subject subj)
         {           
             subj.AimAt(this);
         }
         
         public void Response()
         {
             Console.WriteLine(name + " 老鼠开始逃跑了!");
         }
     }
     public class Master : Observer
     {   
         public Master(Subject subj)
         {           
             subj.AimAt(this);
         }
         
         public void Response()
         {
             Console.WriteLine("主人被惊醒!");
         }  
     }
  
     public class Cat : Subject
     {
         private ArrayList observers;
         public Cat()
         {   
             this.observers = new ArrayList();
         }
         public void AimAt(Observer obs)
         {
             this.observers.Add(obs);
         }
         public void Cry()
         {
             Console.WriteLine("猫叫了!");
             foreach (Observer obs in this.observers)
             {
                 obs.Response();
             }
         }
     }
     class Program
     {       
         static void Main(string[] args)
         {
             Cat cat = new Cat();
             Mouse mouse1 = new Mouse("mouse1", cat);
             Mouse mouse2 = new Mouse("mouse2", cat);
             Master master = new Master(cat);
             cat.Cry();
         }
     }

[csharp] view plain copy
class Program  
{  
    static void Main(string[] args)  
    {  
        Person p = new Person("小李");  
        p.show();  
        Teacher t = new Teacher("小刘",18);  
        t.tshow();  
         
        Console.Read();  
    }  
}  
class Person  
{  
    protected string name;  
    public Person(string name)  
    {  
        this.name = name;  
    }  
    public void show()  
    {  
        Console.WriteLine("我属于人类！");  
    }  
}  
class Teacher:Person  
{  
      
    public Teacher(string name,int age)  
        : base(name)  
    {  
        this.Age = age;  
    }  
    private int _age;  
    public int Age  
    {  
        get { return _age; }   //读  
        set { _age = value; }  //写  
    }  
    public void tshow()  
    {  
        Console.WriteLine("我是学生{0}{1}！",name,Age);          
    }        
}