C# Dictionary通过value获取对应的key值_c#dictionary有value找key

        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
        }