Cache`1.cs

using System;
using System.Collections.Generic;

public class Cache<K, V> where V : class
{
    private readonly Dictionary<K, WeakReference<V>> _data;

    public Cache()
    {
        _data = new Dictionary<K, WeakReference<V>>();
    }

    public void Add(K key, V value)
    {
        _data[key] = new WeakReference<V>(value);
    }

    public void Remove(K key)
    {
        _data.Remove(key);
    }

    public bool TryGetValue(K key, out V result)
    {
        WeakReference<V> weakReference;

        // Does the dictionary contain the key?
        if (_data.TryGetValue(key, out weakReference))
        {
            // Check if the reference target is still alive.
            if (weakReference.TryGetTarget(out result))
            {
                // Found the reference- we're done here.
                return true;
            }
            else
            {
                // Target reference was dead; might as well remove it from
                // the dictionary.
                Remove(key);
                return false;
            }
        }
        else
        {
            // Didn't find anything good, return false.
            result = null;
            return false;
        }
    }
}