C# 中的委托与事件实现灵活的回调机制(应用场景分析)

public delegate void NotifyHandler(string message);

public class Notifier
{
    public event NotifyHandler OnNotify;
    public void TriggerNotification(string message)
    {
        OnNotify?.Invoke(message); // 调用所有订阅者
    }
}
public class Subscriber
{
    public Subscriber(Notifier notifier)
    {
        notifier.OnNotify += HandleNotification;
    }
    private void HandleNotification(string message)
    {
        Console.WriteLine($"Received notification: {message}");
    }
}
// 使用委托
var notifier = new Notifier();
var subscriber = new Subscriber(notifier);
notifier.TriggerNotification("Hello, World!");

Action<string> printAction = Console.WriteLine;
printAction("Hello, World!");

Func<int, int, int> addFunc = (a, b) => a + b;
Console.WriteLine(addFunc(3, 5)); // 输出: 8

public class Publisher
{
    public event EventHandler<EventArgs> SomethingHappened;
    protected virtual void OnSomethingHappened()
    {
        SomethingHappened?.Invoke(this, EventArgs.Empty);
    }
    public void DoSomething()
    {
        // 模拟发生某件事情
        OnSomethingHappened();
    }
}
public class Subscriber
{
    public Subscriber(Publisher publisher)
    {
        publisher.SomethingHappened += Publisher_SomethingHappened;
    }
    private void Publisher_SomethingHappened(object sender, EventArgs e)
    {
        Console.WriteLine("Something happened!");
    }
}
// 使用事件
var publisher = new Publisher();
var subscriber = new Subscriber(publisher);
publisher.DoSomething(); // 触发事件

public class CustomEventArgs : EventArgs
{
    public string Message { get; set; }
}
public class Publisher
{
    public event EventHandler<CustomEventArgs> SomethingHappened;
    protected virtual void OnSomethingHappened(CustomEventArgs e)
    {
        SomethingHappened?.Invoke(this, e);
    }
    public void DoSomething(string message)
    {
        OnSomethingHappened(new CustomEventArgs { Message = message });
    }
}
public class Subscriber
{
    public Subscriber(Publisher publisher)
    {
        publisher.SomethingHappened += Publisher_SomethingHappened;
    }
    private void Publisher_SomethingHappened(object sender, CustomEventArgs e)
    {
        Console.WriteLine($"Publisher says: {e.Message}");
    }
}
// 使用自定义事件参数
var publisher = new Publisher();
var subscriber = new Subscriber(publisher);
publisher.DoSomething("Hello, World!"); // 触发事件并传递信息

button.Click += (sender, e) => MessageBox.Show("Button clicked!");

dataSource.PropertyChanged += (sender, e) => UpdateUI();

logger.Logged += (sender, e) => WriteLogToFile(e.Message);