c# - Dictionary with item limit -

i need provide access key/value pair store persists users across session.

i create singleton this, performance reasons want limit size of dictionary 10000 items (or performant number, object persist indefinitely)

is there form of dictionary can specify limit number of objects stored, , when limit exceeded, remove oldest entry?

there no such built-in dictionary, can build own. need queue keys - allow find oldest entry , remove it. need simple dictionary keeping values - allow search them:

public class superdictionary<tkey, tvalue> {     private dictionary<tkey, tvalue> dictionary;     private queue<tkey> keys;     private int capacity;      public superdictionary(int capacity)     {         this.keys = new queue<tkey>(capacity);         this.capacity = capacity;         this.dictionary = new dictionary<tkey, tvalue>(capacity);     }      public void add(tkey key, tvalue value)     {         if (dictionary.count == capacity)         {             var oldestkey = keys.dequeue();             dictionary.remove(oldestkey);         }          dictionary.add(key, value);         keys.enqueue(key);     }      public tvalue this[tkey key]     {         { return dictionary[key]; }     } } 

note: can implement idictionary<tkey,tvalue> interface, make class 'true' dictionary.