如何让IObservable在订阅时推送最新值

using System;
using System.Collections.Generic;

public interface IObservable
{
    void Subscribe(IObserver observer);
    void UpdateValue(int newValue);
}

public interface IObserver
{
    void Update(int newValue);
}

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

    public void Subscribe(IObserver observer)
    {
        observers.Add(observer);
    }

    public void UpdateValue(int newValue)
    {
        latestValue = newValue;
        foreach (var observer in observers)
        {
            observer.Update(latestValue);
        }
    }
}

public class Observer : IObserver
{
    public void Update(int newValue)
    {
        Console.WriteLine("Received new value: " + newValue);
        // 执行相应的操作
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        Observable observable = new Observable();
        Observer observer = new Observer();

        observable.Subscribe(observer);
        observable.UpdateValue(10); // 输出：Received new value: 10
    }
}