是否存在IDictionary的LRU实现？

using System.Collections.Generic;

public class LRUCache<TKey, TValue>
{
    private readonly int _capacity;
    private readonly Dictionary<TKey, LinkedListNode<CacheItem>> _cache;
    private readonly LinkedList<CacheItem> _lruList;

    public LRUCache(int capacity)
    {
        _capacity = capacity;
        _cache = new Dictionary<TKey, LinkedListNode<CacheItem>>(capacity);
        _lruList = new LinkedList<CacheItem>();
    }

    public TValue Get(TKey key)
    {
        if (_cache.TryGetValue(key, out var node))
        {
            // Move accessed item to the front of the list.
            _lruList.Remove(node);
            _lruList.AddFirst(node);
            return node.Value.Value;
        }

        return default(TValue);
    }

    public void Add(TKey key, TValue value)
    {
        if (_cache.Count >= _capacity)
        {
            // Remove least recently used item.
            var lastNode = _lruList.Last;
            _cache.Remove(lastNode.Value.Key);
            _lruList.RemoveLast();
        }

        // Add new item to the cache and to the front of the list.
        var newNode = new LinkedListNode<CacheItem>(new CacheItem(key, value));
        _cache.Add(key, newNode);
        _lruList.AddFirst(newNode);
    }

    private class CacheItem
    {
        public TKey Key { get; }
        public TValue Value { get; }

        public CacheItem(TKey key, TValue value)
        {
            Key = key;
            Value = value;
        }
    }
}