如何实现IObservable

using System;
using System.Collections.Generic;

public interface IObservable<T>
{
    IDisposable Subscribe(IObserver<T> observer);
}

public interface IObserver<T>
{
    void OnNext(T value);
    void OnError(Exception error);
    void OnCompleted();
}

public class Observable<T> : IObservable<T>
{
    private List<IObserver<T>> observers = new List<IObserver<T>>();

    public IDisposable Subscribe(IObserver<T> observer)
    {
        observers.Add(observer);
        return new Unsubscriber(observers, observer);
    }

    public void Notify(T value)
    {
        foreach (var observer in observers)
        {
            observer.OnNext(value);
        }
    }

    private class Unsubscriber : IDisposable
    {
        private List<IObserver<T>> _observers;
        private IObserver<T> _observer;

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

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

// 使用示例
public class Program
{
    public static void Main()
    {
        var observable = new Observable<int>();

        var observer1 = new Observer<int>("Observer 1");
        var observer2 = new Observer<int>("Observer 2");

        using (observable.Subscribe(observer1))
        {
            observable.Notify(1);
            observable.Notify(2);
            observable.Notify(3);
        }

        observable.Subscribe(observer2);

        observable.Notify(4);
        observable.Notify(5);
        observable.Notify(6);
    }
}

public class Observer<T> : IObserver<T>
{
    private string _name;

    public Observer(string name)
    {
        _name = name;
    }

    public void OnNext(T value)
    {
        Console.WriteLine($"{_name} received value: {value}");
    }

    public void OnError(Exception error)
    {
        Console.WriteLine($"{_name} received an error: {error.Message}");
    }

    public void OnCompleted()
    {
        Console.WriteLine($"{_name} completed");
    }
}