C# Dictionary通過value擷取對應的key值

1：最直白的迴圈遍曆方法，可以分為遍曆key--value索引值對以及所有的key兩種表現形式

2：用Linq的方式去查詢（當然了這裡要添加對應的命名空間 using System.Linq）

 如下為一個十分簡單的程式碼範例：

        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        }

 

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