字典中用于检查键是否存在的逻辑

Question

Dictionary cannot have two values with same key. please tell which logic/algorithm being used in determining whether the key exists or not.

Answer 1

埃里克·利珀特（Eric Lippert）在他的博客文章中详尽地解释了这一点。

Answer 2

How about method ContainsKey of Dictionary?

There are many ways to check for the key but I think this method is most graceful.

Answer 3

Simple put it in try catch

if key exist will remain in try, else if not exists will come in catch

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

string str = "";
try
{
   int a = dic["keytofind"];
   str = "Key Found";
}
catch(Exception)
{
   str = "Key Not Found";
}

Answer 4

Trie data structure is used to store the keys. positive points of using this data structure : 1. Saving of storage space. 2. In O(Log(n)+constant) complexity can be determined about the existence of key.

More details about trie data structure can be found here