问为缓存对象创建单例字典的模式

EN

public class Item
{
    public string key;
    public object obj;
    public Item(string k, object o) { k = key; o = obj; }
}
class MyCache
{
    LinkedList<Item> ll = new LinkedList<Item>();
    LinkedListNode<Item> node;
    Dictionary<string, LinkedListNode<Item>> dd = new Dictionary<string, LinkedListNode<Item>>();
    int capacity = 5;     //just for simplicity set capacity for caching

    //here you Add new object
    public void Add(string key, object obj)
    {
        if (cap == 0) return; 
        //check if you already have that object
        if (!dd.TryGetValue(key, out node)) 
        {
            //if capacity exceeded- remove object from beginig of LinkedList
            if (dd.Count >= capacity) 
                RemoveItem();
            Item item = new Item(key, obj);
            LinkedListNode<Item> newNode = new LinkedListNode<Item>(item);
            ll.AddLast(newNode);
            dd.Add(key, newNode);
            return;
        }
        //we move that object to the end of the list
        ll.Remove(node);
        ll.AddLast(node);
        // we may update value if it was changed, like
        node.Value.obj = obj;
    }

    // remove object from LinkedList and Dictionary
    void RemoveItem()
    {
        LinkedListNode<Item> node = ll.First;
        ll.Remove(node);
        dd.Remove(node.Value.key);
    }

    public object Get(string key)
    { 
        //if we have that object, we return it and move to the end of LList           
        if (dd.TryGetValue(key, out node))
        {
            ll.Remove(node);
            ll.AddLast(node);
            return node.Value.obj;
        }
        else return default(object);
    }
}