首先要理解 State Pattern 模式。

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http://www.dofactory.com/net/state-design-pattern

Definition

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.  

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UML class diagram

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Participants

    The classes and objects participating in this pattern are:

• Context  (Account)
  • defines the interface of interest to clients
  • maintains an instance of a ConcreteState subclass that defines the current state.
• State  (State)
  • defines an interface for encapsulating the behavior associated with a particular state of the Context.
• Concrete State  (RedState, SilverState, GoldState)
  • each subclass implements a behavior associated with a state of Context

先画个状态机用来接收和处理数据。

开始定义Base状态和各个状态

  public abstract class StateBase
    {
public abstract void Enter(Monitor context);

public virtual void Exit(Monitor context)
        {
            Console.WriteLine("Exiting current state: {0}", context.CurrentState.StateName); 
        }

public string StateName
        {
get;
set;
        }
    }

  public class ConnectState : StateBase
    {
public ConnectState()
        {
this.StateName = "Connect"; 
        }
public override void Enter(Monitor context)
        {
            Console.WriteLine("Enter - {0}", context.CurrentState.StateName);
            context.MoveToNextState(new ReceiveDataState()); 
        }
    }

Create a context class, and set initial state to start running.

 public class Monitor
    {
public Monitor()
        {
        }

public void MoveToNextState(StateBase nextState)
        {
            Console.WriteLine("Changing state...");
this.CurrentState.Exit(this);
this.CurrentState = nextState;
this.CurrentState.Enter(this); 
        }

public void Start()
        {
this.CurrentState = new NotStartState();
this.CurrentState.Enter(this); 
        }

public StateBase CurrentState
        {
get;
set;
        }

开始使用状态机

   static void Main(string[] args)
        {
            Monitor m= new Monitor();
            m.Start(); 
        }

网站题目：用StatePattern来实现一个简单的状态机-创新互联
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