public class BaggageInfo
{private int flightNo;private string origin;private int location;internal BaggageInfo(int flight, string from, int carousel){this.flightNo = flight;this.origin = from;this.location = carousel;}public int FlightNumber {get { return this.flightNo; }}public string From {get { return this.origin; }}public int Carousel {get { return this.location; }}
}///
/// 发布者
///
public class BaggageHandler : IObservable<BaggageInfo>
{private List<IObserver<BaggageInfo>> observers;private List<BaggageInfo> flights;public BaggageHandler(){observers = new List<IObserver<BaggageInfo>>();flights = new List<BaggageInfo>();}public IDisposable Subscribe(IObserver<BaggageInfo> observer){// Check whether observer is already registered. If not, add itif (! observers.Contains(observer)) {observers.Add(observer);// Provide observer with existing data.foreach (var item in flights)observer.OnNext(item);}return new Unsubscriber<BaggageInfo>(observers, observer);}// Called to indicate all baggage is now unloaded.public void BaggageStatus(int flightNo){BaggageStatus(flightNo, String.Empty, 0);}public void BaggageStatus(int flightNo, string from, int carousel){var info = new BaggageInfo(flightNo, from, carousel);// Carousel is assigned, so add new info object to list.if (carousel > 0 && ! flights.Contains(info)) {flights.Add(info);foreach (var observer in observers)observer.OnNext(info);}else if (carousel == 0) {// Baggage claim for flight is donevar flightsToRemove = new List<BaggageInfo>();foreach (var flight in flights) {if (info.FlightNumber == flight.FlightNumber) {flightsToRemove.Add(flight);foreach (var observer in observers)observer.OnNext(info);}}foreach (var flightToRemove in flightsToRemove)flights.Remove(flightToRemove);flightsToRemove.Clear();}}public void LastBaggageClaimed(){foreach (var observer in observers)observer.OnCompleted();observers.Clear();}
}
internal class Unsubscriber<BaggageInfo> : IDisposable
{private List<IObserver<BaggageInfo>> _observers;private IObserver<BaggageInfo> _observer;internal Unsubscriber(List<IObserver<BaggageInfo>> observers, IObserver<BaggageInfo> observer){this._observers = observers;this._observer = observer;}public void Dispose() {if (_observers.Contains(_observer))_observers.Remove(_observer);}
}///
/// 订阅者
///
public class ArrivalsMonitor : IObserver<BaggageInfo>
{private string name;private List<string> flightInfos = new List<string>();private IDisposable cancellation;private string fmt = "{0,-20} {1,5}  {2, 3}";public ArrivalsMonitor(string name){if (String.IsNullOrEmpty(name))throw new ArgumentNullException("The observer must be assigned a name.");this.name = name;}public virtual void Subscribe(BaggageHandler provider){cancellation = provider.Subscribe(this);}public virtual void Unsubscribe(){cancellation.Dispose();flightInfos.Clear();}public virtual void OnCompleted() {flightInfos.Clear();}// No implementation needed: Method is not called by the BaggageHandler class.public virtual void OnError(Exception e){// No implementation.
   }// Update information.public virtual void OnNext(BaggageInfo info) {bool updated = false;// Flight has unloaded its baggage; remove from the monitor.if (info.Carousel == 0) {var flightsToRemove = new List<string>();string flightNo = String.Format("{0,5}", info.FlightNumber);foreach (var flightInfo in flightInfos) {if (flightInfo.Substring(21, 5).Equals(flightNo)) {flightsToRemove.Add(flightInfo);updated = true;}}foreach (var flightToRemove in flightsToRemove)flightInfos.Remove(flightToRemove);flightsToRemove.Clear();}else {// Add flight if it does not exist in the collection.string flightInfo = String.Format(fmt, info.From, info.FlightNumber, info.Carousel);if (! flightInfos.Contains(flightInfo)) {flightInfos.Add(flightInfo);updated = true;}}if (updated) {flightInfos.Sort();Console.WriteLine("Arrivals information from {0}", this.name);foreach (var flightInfo in flightInfos)Console.WriteLine(flightInfo);Console.WriteLine();}}
}
using System;
using System.Collections.Generic;public class Example
{public static void Main(){//发布者BaggageHandler provider = new BaggageHandler();// 订阅者ArrivalsMonitor observer1 = new ArrivalsMonitor("BaggageClaimMonitor1");// 订阅者ArrivalsMonitor observer2 = new ArrivalsMonitor("SecurityExit");// 发布provider.BaggageStatus(712, "Detroit", 3);//订阅
        observer1.Subscribe(provider);provider.BaggageStatus(712, "Kalamazoo", 3);provider.BaggageStatus(400, "New York-Kennedy", 1);provider.BaggageStatus(712, "Detroit", 3);observer2.Subscribe(provider);provider.BaggageStatus(511, "San Francisco", 2);provider.BaggageStatus(712);observer2.Unsubscribe();provider.BaggageStatus(400);provider.LastBaggageClaimed();}
}