C#从列表&lt；KeyValuePair&lt；获取键和值。

C# get keys and values from Listlt;KeyValuePairlt;string, stringgt;(C#从列表lt；KeyValuePairlt；获取键和值。)

问题描述

给定列表：

    private List<KeyValuePair<string, string>> KV_List = new List<KeyValuePair<string, string>>();
    void initList()
    {
        KV_List.Add(new KeyValuePair<string, string>("qwer", "asdf"));
        KV_List.Add(new KeyValuePair<string, string>("qwer", "ghjk"));
        KV_List.Add(new KeyValuePair<string, string>("zxcv", "asdf"));
        KV_List.Add(new KeyValuePair<string, string>("hjkl", "uiop"));
    }

(注意：键"q"有多个值，值"asdf"有多个键。)

1)有没有比只对KeyValuePair列表执行Foreach更好的返回所有键列表的方法？

2)类似地，有没有比使用Foreach更好的方法来返回给定键的所有值的列表？

3)然后，返回给定值的键列表如何？

谢谢...

推荐答案

// #1: get all keys (remove Distinct() if you don't want it)
List<string> allKeys = (from kvp in KV_List select kvp.Key).Distinct().ToList();
// allKeys = { "qwer", "zxcv", "hjkl" }

// #2: get values for a key
string key = "qwer";
List<string> values = (from kvp in KV_List where kvp.Key == key select kvp.Value).ToList();
// values = { "asdf", "ghjk" }

// #3: get keys for a value
string value = "asdf";
List<string> keys = (from kvp in KV_List where kvp.Value == value select kvp.Key).ToList();
// keys = { "qwer", "zxcv" }

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