C# 遍历任意字典树结构

发布于 2024-09-03 06:47:48 字数 770 浏览 3 评论 0 原文

我正在尝试编写一个递归 C# 函数，它将对 IDictionary 形式的通用字典进行操作，其中 T 是另一个 IDictionary 或字符串。

我的第一次失败的尝试看起来像这样：

public string HandleDict(IDictionary<string, string> dict){
    // handle the leaf-node here
}

public string HandleDict<T>(IDictionary<string, IDictionary<string, T>> dict){
    // loop through children
    foreach(string key in dict.Keys){
        HandleDict(dict[key]);
    }
}

我还尝试了 HandleDict(IDictionary) 的变体，其中 T : IDictionary 但这也不太有效。我知道我想要做的事情可以通过自定义类作为参数而不是字典来实现，并且我的尝试在概念上是有缺陷的（通用函数中的递归没有尽头）。我仍然想知道是否真的有一种方法可以仅使用通用 IDictionaries 来完成我想要的操作。

原文

I am trying to write a recursive C# function that will operate on generic dictionaries of the form IDictionary<string, T> where T is either another IDictionary<string, T> or a string.

My first failed attempt looked something like this:

public string HandleDict(IDictionary<string, string> dict){
    // handle the leaf-node here
}

public string HandleDict<T>(IDictionary<string, IDictionary<string, T>> dict){
    // loop through children
    foreach(string key in dict.Keys){
        HandleDict(dict[key]);
    }
}

I also tried variants of HandleDict<T>(IDictionary<string, T>) where T : IDictionary<string, T> but that also doesn't quite work. I know that what I want to do could be achieved through a custom class as the parameter instead of dictionaries, and that my attempts are conceptually flawed (there's no end to the recursion in the generic function). I would still like to know if there is actually a way to do what I want here using just generic IDictionaries.

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别闹i 2024-09-10 06:47:48

为了存储字典<字符串，字符串>或或字典作为字典中的值，您需要将字典声明为 Dictionaryobject> 类型。

public string HandleDict(IDictionary<string, object> dict)
{
    foreach (KeyValuePair<string, object> kvp in dict)
    {

然后，您需要检查每个值是否是字符串或另一个 Dictionary或另一个字典 -- C# 在编译时执行重载解析，而不是在运行时！

        var leaf = kvp.Value as IDictionary<string, string>;
        if (leaf != null)
        {
            HandleDict(leaf);
        }
        else
        {
            HandleDict((IDictionary<string, object>)kvp.Value);
        }
    }
}

当到达叶子时，递归将结束，因为 Dictionary 的 HandleDict 重载会导致递归失败。不继续递归。

但是，正如您将注意到的，正在进行大量类型检查和转换，并且 Dictionary 会进行很多类型检查和转换。 闻起来很难闻——它本质上违背了仿制药的目的。

我建议您查看访问者模式。

In order to store either a Dictionary<string, string> or a Dictionary<string,??> as a value in a dictionary, you'd need to declare the dictionary to be of type Dictionary<string, object>.

public string HandleDict(IDictionary<string, object> dict)
{
    foreach (KeyValuePair<string, object> kvp in dict)
    {

Then you'd need to check for each value if it's a string or another Dictionary<string, string> or another Dictionary<string, object> -- C# performs overload resolution at compile-time, not at run-time!

        var leaf = kvp.Value as IDictionary<string, string>;
        if (leaf != null)
        {
            HandleDict(leaf);
        }
        else
        {
            HandleDict((IDictionary<string, object>)kvp.Value);
        }
    }
}

Recursion would end when a leaf is reached, because the HandleDict overload for Dictionary<string, string> does not continue the recursion.

However, as you'll note, there's a lot of type checking and casting going on, and a Dictionary<string, object> smells badly -- it essentially defeats the purpose of generics.

I suggest you have a look at the Visitor Pattern instead.

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