c# - 如何为复杂词典增加值(value)？

Question

据我所知，为字典添加值的方法如下。

    Dictionary<string, string> myDict = new Dictionary<string, string>();

    myDict.Add("a", "1");

如果我将“myDictDict”声明为下面的样式。

IDictionary<string, Dictionary<string, string>> myDictDict = new Dictionary<string, Dictionary<string, string>>();

myDictDict .Add("hello", "tom","cat"); ?// How to add value here.

谢谢你。

Answer 1

正确的做法是这样的:

// myDictDict is Dictionary<string, Dictionary<string, string>>
Dictionary<string, string> myDict;
string key = "hello";
if (!myDictDict.TryGetValue(key, out myDict)) {
    myDict = new Dictionary<string, string>();
    myDictDict.Add(key, myDict);
}
myDict.Add("tom", "cat");

这将提取与键对应的字典(在您的示例中为 hello)或在必要时创建它，然后将键/值对添加到该字典中。您甚至可以将其提取到扩展方法中。

static class Extensions {
    public static void AddToNestedDictionary<TKey, TNestedDictionary, TNestedKey, TNestedValue>(
        this IDictionary<TKey, TNestedDictionary> dictionary,
        TKey key,
        TNestedKey nestedKey,
        TNestedValue nestedValue
    ) where TNestedDictionary : IDictionary<TNestedKey, TNestedValue> {
        dictionary.AddToNestedDictionary(
            key,
            nestedKey,
            nestedValue,
            () => (TNestedDictionary)(IDictionary<TNestedKey, TNestedValue>)
                new Dictionary<TNestedKey, TNestedValue>());
    }

    public static void AddToNestedDictionary<TKey, TNestedDictionary, TNestedKey, TNestedValue>(
        this IDictionary<TKey, TNestedDictionary> dictionary,
        TKey key,
        TNestedKey nestedKey,
        TNestedValue nestedValue,
        Func<TNestedDictionary> provider
    ) where TNestedDictionary : IDictionary<TNestedKey, TNestedValue> {
        TNestedDictionary nested;
        if (!dictionary.TryGetValue(key, out nested)) {
            nested = provider();
            dictionary.Add(key, nested);
        }
        nested.Add(nestedKey, nestedValue);
    }
}

我遗漏了防范 null输入以保持想法清晰。
用法:

myDictDict.AddToNestedDictionary(
    "hello",
    "tom",
    "cat",
    () => new Dictionary<string, string>()
);

或者

myDictDict.AddToNesteDictionary("hello", "tom", "cat");