如何使用的foreach关键字的自定义对象在C＃ [英] How to use foreach keyword on custom Objects in C#

问题描述

有人可以分享使用的foreach 关键字与自定义对象的一个​​简单的例子？

Can someone share a simple example of using the foreach keyword with custom objects?

推荐答案

由于标签，我假设你在.NET中的意思是 - 我会选择谈论C＃，因为这是我所知道的关于

Given the tags, I assume you mean in .NET - and I'll choose to talk about C#, as that's what I know about.

在的foreach 语句（通常）使用的IEnumerable 和的IEnumerator 或他们的共通表兄弟。该形式的语句：

The foreach statement (usually) uses IEnumerable and IEnumerator or their generic cousins. A statement of the form:

foreach (Foo element in source)
{
    // Body
}

其中，源工具的IEnumerable<富> 是的大致的等价于：

where source implements IEnumerable<Foo> is roughly equivalent to:

using (IEnumerator<Foo> iterator = source.GetEnumerator())
{
    Foo element;
    while (iterator.MoveNext())
    {
        element = iterator.Current;
        // Body
    }
}

注意的IEnumerator<富> 设置在年底，不过声明中退出。这是迭代器块重要

Note that the IEnumerator<Foo> is disposed at the end, however the statement exits. This is important for iterator blocks.

要落实的IEnumerable< T> 或的IEnumerator< T> 自己，最简单的方法是使用迭代器块。而不是写在这里所有的细节，它可能最好还是请您先 href=\"http://www.manning.com/skeet\">第六章，这是一个免费下载。第6章的全部是迭代器。我有我的C＃在深入现场另一对夫妇的文章，也：

To implement IEnumerable<T> or IEnumerator<T> yourself, the easiest way is to use an iterator block. Rather than write all the details here, it's probably best to just refer you to chapter 6 of C# in Depth, which is a free download. The whole of chapter 6 is on iterators. I have another couple of articles on my C# in Depth site, too:

• 的迭代器，迭代器块和数据管道


• 的迭代器块实现细节

• Iterators, iterator blocks and data pipelines
• Iterator block implementation details

作为一个简单的例子，但：

As a quick example though:

public IEnumerable<int> EvenNumbers0To10()
{
    for (int i=0; i <= 10; i += 2)
    {
        yield return i;
    }
}

// Later
foreach (int x in EvenNumbers0To10())
{
    Console.WriteLine(x); // 0, 2, 4, 6, 8, 10
}

要落实的IEnumerable< T> 的类型，你可以这样做：

To implement IEnumerable<T> for a type, you can do something like:

public class Foo implements IEnumerable<string>
{
    public IEnumerator<string> GetEnumerator()
    {
        yield return "x";
        yield return "y";
    }

    // Explicit interface implementation for nongeneric interface
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator(); // Just return the generic version
    }
}

这篇关于如何使用的foreach关键字的自定义对象在C＃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！