在C#中,是不是已经使用Events实现的观察者模式？

public class Publisher
{
    public event EventHandler<string> OnMessage;

    public void SendMessage(string message)
    {
        OnMessage?.Invoke(this, message);
    }
}

public class Subscriber
{
    public void Subscribe(Publisher publisher)
    {
        publisher.OnMessage += OnMessageReceived;
    }

    private void OnMessageReceived(object sender, string message)
    {
        Console.WriteLine($"Message received: {message}");
    }
}