C#:将对象添加到队列时触发事件 [英] C#: Triggering an Event when an object is added to a Queue

问题描述

我需要能够在将对象添加到 Queue 时触发事件.

I need to be able to trigger a event whenever an object is added to a Queue<Delegate>.

我创建了一个扩展 Queue 的新类:

I created a new class that extends Queue:

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

public class QueueWithChange<Delegate> : Queue<Delegate>
{
    public event ChangedEventHandler Changed;

    protected virtual void OnChanged(EventArgs e) {
        if (Changed != null)
        {
            Changed(this, e);
        }
    }
}

然后从另一个类附加事件，如下所示:

And then attached the event from another class, like such:

QueueWithChange<TimerDelegate> eventQueue = new QueueWithChange<TimerDelegate>();

//

eventQueue.Changed += new ChangedEventHandler(delegate(object s, EventArgs ex) {
    //This event is not being triggered, so this code is unreachable atm...and that is my problem

    if (eventQueue.Count > 0)
    {
        eventQueue.Dequeue().Invoke(new DispatcherTimer() { Interval = TimeSpan.FromMilliseconds(5) });
        actionTimer.Stop();
    }
});

但是每当我将一个对象排入队列 (eventQueue.Enqueue(something)) 时，附加的事件都不会被触发.

But whenever I enqueue an object (eventQueue.Enqueue(something)), the attached event is not being fired.

我在这里遗漏了什么?

推荐答案

如果你的意思是非通用的 Queue 类，那么你可以重写 Enqueue :

If you mean the non-generic Queue class, then you can just override Enqueue:

public override void Enqueue(object obj)
{
    base.Enqueue(obj);
    OnChanged(EventArgs.Empty);
}

但是，如果您指的是通用的 Queue 类，请注意没有合适的虚方法可以覆盖.您最好用自己的类封装队列:

However, if you mean the generic Queue<T> class, then note that there is no suitable virtual method to override. You might do better to encapsulate the queue with your own class:

(** 重要删除基类！！！**)

(** important edit: removed base-class!!! **)

class Foo<T>
{
    private readonly Queue<T> queue = new Queue<T>();
    public event EventHandler Changed;
    protected virtual void OnChanged()
    {
        if (Changed != null) Changed(this, EventArgs.Empty);
    }
    public virtual void Enqueue(T item)
    {
        queue.Enqueue(item);
        OnChanged();
    }
    public int Count { get { return queue.Count; } }

    public virtual T Dequeue()
    {
        T item = queue.Dequeue();
        OnChanged();
        return item;        
    }
}

但是，查看您的代码，您似乎在这里使用了多个线程.如果是这种情况，请考虑使用线程队列.

However, looking at your code, it seems possible that you are using multiple threads here. If that is the case, consider a threaded queue instead.

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