C# Dictionary通过value获取对应的key值

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

}