辞典项限制 [英] Dictionary with item limit

问题描述

我需要提供访问键/值对商店仍然存在跨会话的所有用户。

I need to provide access to a Key/Value pair store that persists for all users across session.

我可以很容易地创建此单身，但是对于性能原因我想限制字典10000项的大小（或任何高性能的数量，对象将无限期地持续）

I could easily create a singleton for this, but for performance reasons I want to limit the size of the dictionary to 10000 items (or any performant number, as the object will persist indefinitely)

是否有字典的形式，我可以指定限制，以存储对象的数量，超过该限制时，删除最早的项目？

Is there a form of dictionary where I can specify a limit to the number of objects stored, and when that limit is exceeded, remove the oldest entry?

推荐答案

有没有这种内置的字典，但你可以建立自己的。您将需要密钥的队列 - 这将让你迅速找到最旧的条目并删除它。你还需要一个简单的字典保持你的价值观 - 这将允许您快速搜索它们：

There is no such built-in dictionary, but you can build your own. You will need a queue for keys - that will allow you quickly find oldest entry and remove it. Also you will need a simple dictionary for keeping your values - that will allow you quickly search for 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]
    {
        get { return dictionary[key]; }
    }
}

请注意：您可以实施 IDictionary的< TKEY的，TValue方式> 接口，使这一类真实字典

NOTE: You can implement IDictionary<TKey,TValue> interface, to make this class a 'true' dictionary.

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