Reto 6 MSDN http://blogs.msdn.com/b/esmsdn/archive/2014/11/14/retosmsdn-reto-6-cach-233-de-objetos-en-c.aspx

Cache.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace Reto_6
{

    [DebuggerDisplay("Count = {Count}, ActiveCount = {ActiveCount}")]
    [DebuggerTypeProxy(typeof(CacheDebugView))]
    public class Cache
    {
        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        private readonly Dictionary<object, WeakReference> dict = new Dictionary<object, WeakReference>(); 

        public void Add(object key, object value) {
            dict.Add(key, new WeakReference(value));
        }

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        public int Count {
            get { return dict.Count; }        
        }

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        public int ActiveCount {
            get { return dict.Values.Count(x => x.Target != null); }
        }

        public object this[object key] {
            get { return dict[key].Target; }
        }


        [DebuggerDisplay("Key = {Key}, Value = {Value}")]
        internal class Pair
        {
            [DebuggerBrowsable(DebuggerBrowsableState.Never)]
            public object Key { get; set; }
            
            [DebuggerBrowsable(DebuggerBrowsableState.Never)]
            public object Value { get; set; }
        }

        internal class CacheDebugView
        {
            [DebuggerBrowsable(DebuggerBrowsableState.Never)]
            private readonly Cache cache;
            
            public CacheDebugView(Cache cache) {
                this.cache = cache;
            }

            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
            public Pair[] Pairs {
                get {
                    return cache.dict.Select(x => new Pair {Key = x.Key, Value = x.Value.Target}).ToArray();
                }
            }
        }
    }
}