Question

C#如何通过Key键获取Dictionary集合内的Value？

Answer 1

var dic = new Dictionary<string, int>() { {"a",1}, {"b",2}, {"c",3}, {"d",1} }; foreach (var item in dic) { if (item.Value == 1) { Console.WriteLine(item.Key); } }

1.最直白的循环遍历方法，可以分为遍历key--value键值对以及所有的key两种表现形式

2.用Linq的方式去查询（当然了这里要添加对应的命名空间 using System.Linq）

如下为一个十分简单的代码示例：

private void GetDicKeyByValue()

{

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

dic.Add("1", "1");

dic.Add("2", "2");

dic.Add("3", "2");

//foreach KeyValuePair traversing

foreach (KeyValuePair<string, string> kvp in dic)

{

if (kvp.Value.Equals("2"))

{ 

//...... kvp.Key;

}

}

//foreach dic.Keys

foreach (string key in dic.Keys)

{

if (dic[key].Equals("2"))

{ 

//...... key

}

}

//Linq

var keys = dic.Where(q => q.Value == "2").Select(q => q.Key);  //get all keys

List<string> keyList = (from q in dic

where q.Value == "2"

select q.Key).ToList<string>(); //get all keys

var firstKey = dic.FirstOrDefault(q => q.Value == "2").Key;  //get first key

}