如何处理添加到列表事件? [英] How to handle add to list event?

问题描述

我有一个这样的列表:

List<Controls> list = new List<Controls>

如何处理向此列表添加新位置?

How to handle adding new position to this list?

当我这样做时:

myObject.myList.Add(new Control());

我想在我的对象中做这样的事情:

I would like to do something like this in my object:

myList.AddingEvent += HandleAddingEvent

然后在我的 HandleAddingEvent 委托处理中添加位置到这个列表.我应该如何处理添加新位置事件?我怎样才能使这个活动可用?

And then in my HandleAddingEvent delegate handling adding position to this list. How should I handle adding new position event? How can I make this event available?

推荐答案

您可以从 List 继承并添加您自己的处理程序，例如

You could inherit from List and add your own handler, something like

using System;
using System.Collections.Generic;

namespace test
{
    class Program
    {

        class MyList<T> : List<T>
        {

            public event EventHandler OnAdd;

            public new void Add(T item) // "new" to avoid compiler-warnings, because we're hiding a method from base-class
            {
                if (null != OnAdd)
                {
                    OnAdd(this, null);
                }
                base.Add(item);
            }
        }

        static void Main(string[] args)
        {
            MyList<int> l = new MyList<int>();
            l.OnAdd += new EventHandler(l_OnAdd);
            l.Add(1);
        }

        static void l_OnAdd(object sender, EventArgs e)
        {
            Console.WriteLine("Element added...");
        }
    }
}

警告

1. 请注意，您必须重新实现所有将对象添加到列表中的方法.AddRange() 在这个实现中不会触发这个事件.

1. Be aware that you have to re-implement all methods which add objects to your list. AddRange() will not fire this event, in this implementation.

我们没有超载该方法.我们把原来的藏了起来.如果你Add()一个对象，而这个类在List中被装箱，事件将不会被触发!

We did not overload the method. We hid the original one. If you Add() an object while this class is boxed in List<T>, the event will not be fired!

MyList<int> l = new MyList<int>();
l.OnAdd += new EventHandler(l_OnAdd);
l.Add(1); // Will work

List<int> baseList = l;
baseList.Add(2); // Will NOT work!!!

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