如何在 .NET 2.0 中创建自定义集合

问题描述

我想创建我的自定义集合，我正在从 CollectionBase 类派生我的自定义集合类，如下所示:

Hi I want to create my custom collection, I am deriving my custom collection class from CollectionBase class as below:

public class MyCollection : System.Collectio.CollectionBase
{
    MyCollection(){}
    public void Add(MyClass item)
    {
        this.List.Add(item);
    }
}

class MyClass
{
    public string name;
}

让我问几个问题:

1. 这种方法是否正确且新颖，因为我正在研究 .NET 3.5 框架.
2. 我想从我的网络服务 (WCF) 中公开这个集合.我该怎么做?
3. 我是否必须实施 GetEnumerator?
4. 这是否会绑定到 DataGridView.

推荐答案

从 List 派生有点毫无意义，尤其现在它有了 IEnumerable 构造函数和扩展方法的可用性.除了 Equals、GetHashCode 和 ToString 之外，它没有可以覆盖的虚拟方法.(如果您的目标是为列表实现 Java 的 toString() 功能，我想您可以从 List 派生.)

Deriving from List<T> is somewhat pointless, especially now that it has the IEnumerable<T> constructor and the availability of extension methods. It has no virtual methods that you can override except Equals, GetHashCode, and ToString. (I suppose you could derive from List<T> if your goal was to implement Java's toString() functionality for lists.)

如果您想创建自己的强类型集合类并可能在添加/删除项目时自定义集合行为，您希望从新的(到 .NET 2.0)类型派生 System.Collections.ObjectModel.Collection，有保护虚方法包括 InsertItem 和 RemoveItem，您可以覆盖它们以在这些时间执行操作.请务必阅读文档 - 这是一个非常容易派生的类，但您必须意识到公共/非虚拟方法和受保护/虚拟方法之间的区别.:)

If you want to create your own strongly-typed collection class and possibly customize the collection behavior when items are add/removed, you want to derive from the new (to .NET 2.0) type System.Collections.ObjectModel.Collection<T>, which has protected virtual methods including InsertItem and RemoveItem that you can override to perform actions at those times. Be sure to read the documentation - this is a very easy class to derive from but you have to realize the difference between the public/non-virtual and protected/virtual methods. :)

public class MyCollection : Collection<int>
{
    public MyCollection()
    {
    }

    public MyCollection(IList<int> list)
        : base(list)
    {
    }

    protected override void ClearItems()
    {
        // TODO: validate here if necessary
        bool canClearItems = ...;
        if (!canClearItems)
            throw new InvalidOperationException("The collection cannot be cleared while _____.");

        base.ClearItems();
    }

    protected override void RemoveItem(int index)
    {
        // TODO: validate here if necessary
        bool canRemoveItem = ...;
        if (!canRemoveItem)
            throw new InvalidOperationException("The item cannot be removed while _____.");

        base.RemoveItem(index);
    }
}

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