C#设计模式之行为型模式详解

来源：本站原创|时间：2020-01-10|栏目：C#教程|点击：次

这里列举行为型模式·到此23种就列完了···这里是看着菜鸟教程来实现··，他里边列了25种，其中过滤器模式和空对象模式应该不属于所谓的23种模式

责任链模式：为请求创建一个接收者对象的链，对请求的发送者和接收者进行解耦，大部分用于web中吧。。
Task中的continuewith和微软的tpl数据流应该是类似这种模式的实现吧

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//责任链模式
namespace ExercisePrj.Dsignmode
{
  public abstract class AbstractLogger
  {
    public static int INFO = 1;
    public static int DEBUG = 2;
    public static int ERROR = 3;
    protected int level;
    //责任链中的下一个对象
    protected AbstractLogger nextLogger;
    public void SetNextLogger(AbstractLogger next)
    {
      nextLogger = next;
    }
    public void LogMessage(int level,string message)
    {
      if(this.level<=level)
      {
        Write(message);
      }
      if(nextLogger!=null)
      {
        nextLogger.LogMessage(level, message);
      }
    }
    protected abstract void Write(string message);
  }
  public class ConsoleLogger : AbstractLogger
  {

    public ConsoleLogger(int level)
    {
      this.level = level;
    }

    protected override void Write(string message)
    {
      Console.WriteLine("Standard Console::Logger: " + message);
    }
  }
  public class ErrorLogger : AbstractLogger
  {

    public ErrorLogger(int level)
    {
      this.level = level;
    }

    protected override void Write(String message)
    {
      Console.WriteLine("Error Console::Logger: " + message);
    }
  }
  public class FileLogger : AbstractLogger
  {
    public FileLogger(int level)
    {
      this.level = level;
    }

    protected override void Write(String message)
    {
      Console.WriteLine("File::Logger: " + message);
    }
  }
}

命令模式（Command Pattern）:请求以命令的形式执行，CAD的的命令应该就是以这种方式执行的·二次开发的时候通过特性标识和继承他的接口来添加命令，非常方便

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//命令模式
namespace ExercisePrj.Dsignmode
{
  public interface IOrder
  {
    void Execute();
  }
  public class Stock
  {
    private string name = "ABC";
    private int quantity = 10;

    public void Buy()
    {
      Console.WriteLine("Stock name:{0},quantity:{1},bought",name,quantity);
    }
    public void Sell()
    {
      Console.WriteLine("Stock name:{0},quantity:{1}sold", name, quantity);
    }
  }
  //请求类
  public class BuyStock : IOrder
  {
    private Stock abcStock;

    public BuyStock(Stock abcStock)
    {
      this.abcStock = abcStock;
    }

    public void Execute()
    {
      abcStock.Buy();
    }
  }
  //继承接口的实体
  public class SellStock : IOrder
  {
    private Stock abcStock;

    public SellStock(Stock abcStock)
    {
      this.abcStock = abcStock;
    }

    public void Execute()
    {
      abcStock.Sell();
    }
  }

  //命令调用类
  public class Broker
  {
    private List<IOrder> orderList = new List<IOrder>();

    public void takeOrder(IOrder order)
    {
      orderList.Add(order);
    }

    public void placeOrders()
    {
      foreach (IOrder order in orderList)
      {
        order.Execute();
      }
      orderList.Clear();
    }
  }

}

解释器模式：就是实现一种表达式接口，C#的各种表达式就是这种实现吧··这玩意跟富文本编辑器一样是个大坑吧··，做好了确实很好使，一不小心就得跪

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//解释器模式
namespace ExercisePrj.Dsignmode
{
  public interface Expression
  {
     bool Interpret(string context);
  }
  public class TerminalExpression : Expression
  {
    private string data;

    public TerminalExpression(string data)
    {
      this.data = data;
    }

    public bool Interpret(string context)
    {
      if (context.Contains(data))
      {
        return true;
      }
      return false;
    }
  }
  public class OrExpression : Expression
  {
    private Expression expr1 = null;
    private Expression expr2 = null;
    public OrExpression(Expression expr1, Expression expr2)
    {
      this.expr1 = expr1;
      this.expr2 = expr2;
    }
    public bool Interpret(String context)
    {
      return expr1.Interpret(context) || expr2.Interpret(context);
    }
  }
  public class AndExpression : Expression
  {
    private Expression expr1 = null;
    private Expression expr2 = null;

    public AndExpression(Expression expr1, Expression expr2)
    {
      this.expr1 = expr1;
      this.expr2 = expr2;
    }
    public bool Interpret(String context)
    {
      return expr1.Interpret(context) && expr2.Interpret(context);
    }
    }
}

迭代器模式（Iterator Pattern）：.NET自带接口···，直接实现就行了··注意又泛型接口和非泛型接口··非泛型接口迭代对象返回的是object，泛型接口返回的直接就是对象了，还有通过yield的简化写法不用额外去实现IEnumerator接口

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

namespace ExercisePrj.Dsignmode
{
  public class IteratorEx : IEnumerable //<IteratorEx>
  {
    public string Name;
    private List<IteratorEx> list = new List<IteratorEx>();

    //public IEnumerator<IteratorEx> GetEnumerator()
    //{
    //  foreach (var l in list)
    //  {
    //    yield return l;
    //  }
    //}

    public void SetList(List<IteratorEx> data)
    {
      list = data;
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
      foreach (var l in list)
      {
        yield return l;
      }
      //return new IteratorExEnum(list.ToArray());
    }
  }
  public class IteratorExEnum : IEnumerator
  {
    private IteratorEx[] list;
    private int position = -1;
    public IteratorExEnum(IteratorEx[] data)
    {
      list = data;
    }
    public object Current
    {
      get
      {
        try
        {
          return list[position];
        }
        catch (IndexOutOfRangeException)
        {
          throw new InvalidOperationException();
        }
      }
    }

    public bool MoveNext()
    {
      position++;
      return position < list.Length;
    }

    public void Reset()
    {
      position = -1;
    }
  }

}

中介者模式（Mediator Pattern）：用一个中介对象封装一些对象的交互，中介者使对象不用显式的互相引用，MVC和mvp 的c和p都是类似这玩意的实现吧

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

namespace ExercisePrj.Dsignmode
{
  //中介类
  public class ChatRoom
  {
    public static void ShowMessage(User user, string msg)
    {
      Console.WriteLine(new DateTime().ToString()+"["+ user.Name + "] : " + msg);
    }
  }
  public class User
  {
    public string Name { get; set; }

    public User(string name)
    {
      Name = name;
    }

    public void SendMessage(String message)
    {
      ChatRoom.ShowMessage(this, message);
    }
  }


}

备忘录模式（Memento Pattern）：在不破坏封装的前提下，捕获一个对象的内部状态，并在对象之外保存，

大部分支持回退的操作场景下应该都是这种模式··之前做的软件中有画图的操作···支持后退，实现方式非常简单粗暴··，直接吧图层的画图对象克隆一份保存··只支持5还是10步，讲道理这么实现确实有点那啥了···

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

namespace ExercisePrj.Dsignmode
{
  public class Memento
  {
    public string State { get; }
    public Memento(string state)
    {
      State = state;
    }
  }
  public class Originator
  {
    public string State { get; set; }

    public Memento SaveStateToMemento()
    {
      return new Memento(State);
    }

    public void GetStateFromMemento(Memento Memento)
    {
      State = Memento.State;
    }
  }
  public class CareTaker
  {
    private List<Memento> mementoList = new List<Memento>();

    public void Add(Memento state)
    {
      mementoList.Add(state);
    }

    public Memento Get(int index)
    {
      return mementoList[index];
    }
  }

}

观察者模式（Observer Pattern）：.net自带的有接口提供来实现观察者模式···这里照着msdn来实现一遍，自带的接口里边还实现了资源的释放··，之前并发编程里边的rx也是这个模式的具体实现·

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

//观察者模式
namespace ExercisePrj.Dsignmode
{

  public class Subject: IObservable<Subject>
  {
    public int State {get; set;}
    public Subject(int state)
    {
      State = state;
    }
    private List<IObserver<Subject>> observers = new List<IObserver<Subject>>();

    public IDisposable Subscribe(IObserver<Subject> observer)
    {
      if (!observers.Contains(observer))
        observers.Add(observer);
      return new Unsubscriber(observers, observer);
    }
    private class Unsubscriber : IDisposable
    {
      private List<IObserver<Subject>> _observers;
      private IObserver<Subject> _observer;

      public Unsubscriber(List<IObserver<Subject>> observers, IObserver<Subject> observer)
      {
        this._observers = observers;
        this._observer = observer;
      }

      public void Dispose()
      {
        if (_observer != null && _observers.Contains(_observer))
          _observers.Remove(_observer);
      }
    }

    public void TrackLocation(Subject ob)
    {
      Console.WriteLine("start");
      foreach (var observer in observers)
      {
        if (ob==null)
          observer.OnError(new Exception("unknowExeption"));
        else
          observer.OnNext(ob);
      }
    }

    public void EndTransmission()
    {
      foreach (var observer in observers.ToArray())
        if (observers.Contains(observer))
          observer.OnCompleted();

      observers.Clear();
    }

  }


  public class BinaryObserver : IObserver<Subject>
  {
    public void OnCompleted()
    {
      Console.WriteLine("complete");
    }

    public void OnError(Exception error)
    {
      Console.WriteLine(error.Message);
    }

    public void OnNext(Subject value)
    {
      Console.WriteLine("Binary String: " + Convert.ToString(value.State, 2));
    }
  }
  public class OctalObserver : IObserver<Subject>
  {
    public void OnCompleted()
    {
      Console.WriteLine("complete");
    }

    public void OnError(Exception error)
    {
      Console.WriteLine(error.Message);
    }

    public void OnNext(Subject value)
    {
      Console.WriteLine("Octal String: " + Convert.ToString(value.State, 8));
    }

  }
  public class HexaObserver : IObserver<Subject>
  {
    public void OnCompleted()
    {
      Console.WriteLine("complete");
    }

    public void OnError(Exception error)
    {
      Console.WriteLine(error.Message);
    }

    public void OnNext(Subject value)
    {
      Console.WriteLine("Hex String: " + Convert.ToString(value.State,16));
    }
  }
}

状态模式（State Pattern）：当对象内部状态发生改变时，行为也跟着改变

这个模式是为了解决类里边的大量if和swicth语句，讲道理例子写的有点怪···主体是context

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

namespace ExercisePrj.Dsignmode
{
  public class Context
  {
    public State State { get; set; }

    public Context()
    {
      State = null;
    }
  }
  public interface State
  {
     void DoAction(Context context);
  }

  public class StartState : State
  {
    public void DoAction(Context context)
    {
      Console.WriteLine("Player is in start state");
      context.State = this;
    }

    public override string ToString()
    {
      return "Start State";
    }
  }
  public class StopState : State
  {

    public void DoAction(Context context)
    {
      Console.WriteLine("Player is in stop state");
      context.State = this;
    }

    public override string ToString()
    {
      return "Stop State";
    }
  }
}

空对象模式（Null Object Pattern）：就是吧对空值的判断定义一个啥也不做的实体对象出来··C#的Nullable就是这个的实现···这玩意不在23种设计模式里边···

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

namespace ExercisePrj.Dsignmode
{
  public abstract class AbstractCustomer
  {
    public abstract bool IsNull();
    public abstract string Name { get; }
  }
  public class RealCustomer : AbstractCustomer
  {
    public override string Name { get; }

    public RealCustomer(string name)
    {
      Name = name;
    }
    public override bool IsNull()
    {
      return false;
    }
  }
  public class NullCustomer : AbstractCustomer
  {
      public override string Name { get { return "Not Available in Customer Database"; } }
      public override bool IsNull()
      {
        return true;
      }
  }
  public class CustomerFactory
  {
    public static string[] names = {"Rob", "Joe", "Julie"};
     public static AbstractCustomer getCustomer(string name)
    {
      if(names.Contains(name))
      {
        return new RealCustomer(name);
      }
      return new NullCustomer();
    }
  }
}

策略模式（Strategy Pattern）：定义一系列算法，封装成类，可以相互替换，通过构造不同的类，执行不同的操作。这样做方便调用，添加新的算法也方便，

最后加了自己之前对这个模式的奇葩写法

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

namespace ExercisePrj.Dsignmode
{
  public interface IStrategy
  {
     int DoOperation(int num1, int num2);
  }
  public class OperationAdd : IStrategy
  {
    
    public int DoOperation(int num1, int num2)
    {
      return num1 + num2;
    }
  }

  public class OperationSubstract : IStrategy
  {

    public int DoOperation(int num1, int num2)
    {
      return num1 - num2;
    }
  }
  public class OperationMultiply : IStrategy
  {

    public int DoOperation(int num1, int num2)
    {
       return num1 * num2;
    }
  }

  public class ContextEx
  {
    private IStrategy strategy;

    public ContextEx(IStrategy strategy)
    {
      this.strategy = strategy;
    }

    public int ExecuteStrategy(int num1, int num2)
    {
      return strategy.DoOperation(num1, num2);
    }

    //奇葩的写法简单粗暴
    private Dictionary<string, Func<int, int, int>> funcs = new Dictionary<string, Func<int, int, int>>();
    public int ExecuteStrategy(string name, int num1, int num2)
    {
      if(funcs.Count==0)
      {
        //反射写法
        var assembly = Assembly.GetExecutingAssembly();
        var types = assembly.GetTypes();
        foreach (var t in types)
        {
          if (t.GetInterface("IStrategy") != null)
          {
            var instance = assembly.CreateInstance(t.FullName) as IStrategy;
            funcs.Add(t.Name, instance.DoOperation);
          }
        }
        //直接添加
        //funcs.Add("OperationAdd", new Func<int, int, int>((n1, n2) => { return n1 + n2; }));
        //funcs.Add("OperationSubstract", new Func<int, int, int>((n1, n2) => { return n1 - n2; }));
        //funcs.Add("OperationMultiply", new Func<int, int, int>((n1, n2) => { return n1 * n2; }));
      }
      return funcs[name](num1, num2);
    }


  }
}

模板模式（Template Pattern）：.net的泛型就是这个模式的实现吧··照着模子写就行了

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

namespace ExercisePrj.Dsignmode
{
  public abstract class Game
  {
    public abstract void Initialize();
    public abstract void StartPlay();
    public abstract void EndPlay();

    //模板
    public void play()
    {

      //初始化游戏
      Initialize();
      //开始游戏
      StartPlay();
      //结束游戏
      EndPlay();
    }
  }
  public class Cricket : Game
  {
    public override void EndPlay()
    {
      Console.WriteLine("Cricket Game Finished!");
    }

    public override void Initialize()
    {
      Console.WriteLine("Cricket Game Initialized! Start playing.");
    }


    public override void StartPlay()
    {
      Console.WriteLine("Cricket Game Started. Enjoy the game!");
    }
  }
}

访问者模式（Visitor Pattern）：在被访问的类里边加一个对外提供接待访问的接口
把数据结构和对应的操作分开·添加操作很容易，但是如果结构变化多的化，改起来就麻烦了··
没研究没用过····

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

namespace ExercisePrj.Dsignmode
{

  public interface IComputerPartVisitor
  {
    void Visit(Computer computer);
    void Visit(Mouse mouse);
    void Visit(Keyboard keyboard);
    void Visit(Monitor monitor);
  }

  public interface IComputerPart
  {
    void Accept(IComputerPartVisitor computerPartVisitor);
  }

  public class Keyboard : IComputerPart
  {

    public void Accept(IComputerPartVisitor computerPartVisitor)
    {
      computerPartVisitor.Visit(this);
    }
  }
  public class Monitor : IComputerPart
  {

    public void Accept(IComputerPartVisitor computerPartVisitor)
    {
      computerPartVisitor.Visit(this);
    }
}
  public class Mouse : IComputerPart
  {
    public void Accept(IComputerPartVisitor computerPartVisitor)
    {
      computerPartVisitor.Visit(this);
    }
  }
  public class Computer : IComputerPart
  {
    IComputerPart [] parts;
    public Computer()
    {
      parts = new IComputerPart[] { new Mouse(), new Keyboard(), new Monitor() };
    }
    public void Accept(IComputerPartVisitor computerPartVisitor)
    {
      for (int i = 0; i < parts.Length; i++)
      {
        parts[i].Accept(computerPartVisitor);
      }
      computerPartVisitor.Visit(this);
    }
  }

  public class ComputerPartDisplayVisitor : IComputerPartVisitor
  {
    public void Visit(Computer computer)
    {
      Console.WriteLine("Displaying Computer.");
    }
    public void Visit(Mouse mouse)
    {
      Console.WriteLine("Displaying Mouse.");
    }
    public void Visit(Keyboard keyboard)
    {
      Console.WriteLine("Displaying Keyboard.");
    }
    public void Visit(Monitor monitor)
    {
      Console.WriteLine("Displaying Monitor.");
    }
  }
}

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