C＃从字典继承，遍历KeyValuePairs [英] C# inherit from Dictionary, iterate over KeyValuePairs

问题描述

我有一个类从继承字典＆LT;字符串，字符串＆GT; 。在实例方法，我想遍历所有 KeyValuePair＆LT;字符串，字符串＆GT; 的。我试着做以下几点：

I have a class that inherits from Dictionary<string, string>. Within an instance method, I want to iterate over all KeyValuePair<string, string>'s. I've tried doing the following:

foreach (KeyValuePair<string, string> pair in base)

但这种失败，出现以下错误：

But this fails with the following error:

关键字'基地'的使用无效在这种情况下

Use of keyword 'base' is not valid in this context

我怎么能遍历 KeyValuePair＆LT;字符串，字符串＆GT; 的一个实例方法，从派生的类字典＆LT;字符串，字符串＆GT;

How can I iterate over the KeyValuePair<string, string>'s in an instance method in a class that derives from Dictionary<string, string>?

编辑：我发现我能做到以下几点：

I found I can do the following:

var enumerator = base.GetEnumerator();
while (enumerator.MoveNext())
{
    KeyValuePair<string, string> pair = enumerator.Current;
}

不过，我还是想知道，如果有一种方法通过的foreach 循环来做到这一点。

编辑：感谢约不是从词典＆LT继承了意见;字符串，字符串＆GT; 。我代替实施 System.Collections.IEnumerable，ICollection的＆LT; KeyValuePair＆LT;字符串，字符串＆GT;＆gt;中的IEnumerable＆LT; KeyValuePair＆LT;字符串，字符串＆GT;＆gt;中的IDictionary＆LT;字符串，字符串＆GT; 。

thanks for the advice about not inheriting from Dictionary<string, string>. I'm instead implementing System.Collections.IEnumerable, ICollection<KeyValuePair<string, string>>, IEnumerable<KeyValuePair<string, string>>, IDictionary<string, string>.

推荐答案

首先，从.NET集合类派生一般是不明智的，因为他们不提供没有从继承调用虚拟方法对象。通过一个基类的引用传递派生集合时某处这可能会导致错误。你最好还是实施的IDictionary＆LT; T，TKEY的＆GT; 接口和聚合一个词典＆LT;，＆GT; 你里面执行 - 为你再往前适当的调用

First, deriving from the .NET collection classes is generally ill-advised because they don't offer virtual methods for calls not inherited from object. This can result in bugs when passing your derived collection in via a base-class reference somewhere. You are better off implementing the IDictionary<T,TKey> interface and aggregating a Dictionary<,> inside your implementation - to which you then forward the appropriate calls.

除此之外，在特定的情况下，你想要做的是：

That aside, in your specific case, what you want to do is:

foreach( KeyValuePair<string,string> pair in this )  { /* code here */ }

的基关键字主要是用来访问你的基类的特定成员。这不是你在这里做什么 - 你正试图遍历特定实例的物品......这简直是在这个引用

The base keyword is primarily used to access specific members of your base class. That's not what you're doing here - you are attempting to iterate over the items of a particular instance ... which is simply the this reference.

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