C# EventHandler的使用详解(最新整理)

public delegate void EventHandler(object sender, EventArgs e);

public class Publisher
{
    // 定义事件 - 无数据事件
    public event EventHandler MyEvent;
    // 触发事件的方法（推荐使用空值检查）
    protected virtual void OnMyEvent()
    {
        MyEvent?.Invoke(this, EventArgs.Empty);
    }
    // 触发事件的公共方法
    public void TriggerEvent()
    {
        OnMyEvent();
    }
}

public class Subscriber
{
    public void HandleMyEvent(object sender, EventArgs e)
    {
        Console.WriteLine("事件已触发!");
        // 可以访问sender对象，如：((Publisher)sender).SomeProperty
    }
}

public class Program
{
    static void Main()
    {
        Publisher publisher = new Publisher();
        Subscriber subscriber = new Subscriber();
        // 注册事件处理程序
        publisher.MyEvent += subscriber.HandleMyEvent;
        // 触发事件
        publisher.TriggerEvent();
        // 可选：移除事件处理程序
        publisher.MyEvent -= subscriber.HandleMyEvent;
    }
}

// 自定义事件参数类
public class CustomEventArgs : EventArgs
{
    public string Message { get; set; }
    public int Value { get; set; }
}
// 发布者类
public class DataPublisher
{
    public event EventHandler<CustomEventArgs> DataProcessed;
    protected virtual void OnDataProcessed(CustomEventArgs e)
    {
        DataProcessed?.Invoke(this, e);
    }
    public void ProcessData(string message, int value)
    {
        // 处理数据...
        OnDataProcessed(new CustomEventArgs { Message = message, Value = value });
    }
}
// 订阅者
public class DataSubscriber
{
    public void HandleDataProcessed(object sender, CustomEventArgs e)
    {
        Console.WriteLine($"收到数据: {e.Message}, 值: {e.Value}");
    }
}

// 错误示范（可能导致异常）
MyEvent(this, EventArgs.Empty); 
// 正确做法（空值检查）
MyEvent?.Invoke(this, EventArgs.Empty);

// 线程安全的事件触发
var handler = Volatile.Read(ref MyEvent);
handler?.Invoke(this, EventArgs.Empty);

publisher.MyEvent += (sender, e) => 
{
    Console.WriteLine("通过Lambda处理事件");
};

// 在订阅者销毁时注销事件
public class Subscriber : IDisposable
{
    private Publisher _publisher;
    public Subscriber(Publisher publisher)
    {
        _publisher = publisher;
        _publisher.MyEvent += HandleEvent;
    }
    public void Dispose()
    {
        _publisher.MyEvent -= HandleEvent;
    }
    private void HandleEvent(object sender, EventArgs e)
    {
        // 事件处理逻辑
    }
}

public class Publisher
{
    // 使用EventHandler作为委托类型定义事件
    public event EventHandler MyEvent;
    protected virtual void OnMyEvent()
    {
        MyEvent?.Invoke(this, EventArgs.Empty);
    }
}

public class Button
{
    public event EventHandler Click;
    public void OnClick()
    {
        Click?.Invoke(this, EventArgs.Empty);
    }
}
public class Form
{
    public void Initialize()
    {
        Button button = new Button();
        // 使用EventHandler注册事件处理
        button.Click += (sender, e) => Console.WriteLine("Button clicked!");
    }
}

// 创建事件
AutoResetEvent autoEvent = new AutoResetEvent(false);
// 线程1：等待事件
Thread thread1 = new Thread(() =>
{
    Console.WriteLine("Thread 1: Waiting for event...");
    autoEvent.WaitOne();
    Console.WriteLine("Thread 1: Event received!");
});
// 线程2：触发事件
Thread thread2 = new Thread(() =>
{
    Thread.Sleep(2000);
    Console.WriteLine("Thread 2: Setting event...");
    autoEvent.Set();
});
thread1.Start();
thread2.Start();