WeakReference Class

using System;
using System.Collections.Generic;

public class Program
{

    public static void Main()
    {

        // Create the cache.
        int cacheSize = 50;
        Random r = new Random();
        Cache c = new Cache(cacheSize);

        string DataName = "";

        // Randomly access objects in the cache.
        for (int i = 0; i < c.Count; i++)
        {
            int index = r.Next(c.Count);

            // Access the object by
            // getting a property value.
            DataName = c[index].Name;
        }
        // Show results.
        double regenPercent = c.RegenerationCount * 100 / c.Count;
        Console.WriteLine("Cache size: {0}, Regenerated: {1}%", c.Count.ToString(), regenPercent.ToString());

    }
}


public class Cache
{
    // Dictionary to contain the cache.
    static Dictionary<int, WeakReference> _cache;

    // Track the number of times an 
    // object is regenerated.
    int regenCount = 0;   

    public Cache(int count)
    {

        _cache = new Dictionary<int, WeakReference>();

        // Add data objects with a 
        // short weak reference to the cache.
       for (int i = 0; i < count; i++)
        {
            _cache.Add(i, new WeakReference(new Data(i), false));
        }

    }

    // Returns the number of items in the cache.
    public int Count
    {
        get
        {
            return _cache.Count;
        }
    }

    // Returns the number of times an 
    // object had to be regenerated.
    public int RegenerationCount
    {
        get
        {
            return regenCount;
        }
    }

    // Accesses a data object from the cache.
    // If the object was reclaimed for garbage collection,
    // create a new data object at that index location.
    public Data this[int index]
    {
        get
        {
            // Obtain an instance of a data
            // object from the cache of
            // of weak reference objects.
            Data d = _cache[index].Target as Data;
            if (d == null)
            {
                // Object was reclaimed, so generate a new one.
                Console.WriteLine("Regenerate object at {0}: Yes", index.ToString());
                d = new Data(index);
                regenCount++;
            }
            else
            {
                // Object was obtained with the weak reference.
                Console.WriteLine("Regenerate object at {0}: No", index.ToString());
            }

            return d;
       }

    }

}


// This class creates byte arrays to simulate data.
public class Data
{
    private byte[] _data;
    private string _name;

    public Data(int size)
    {
        _data = new byte[size * 1024];
        _name = size.ToString();
    }

    // Simple property.
    public string Name
    {
        get
        {
            return _name;
        }
    }

}

// Example of the last lines of the output:
//
// ...
// Regenerate object at 36: Yes
// Regenerate object at 8: Yes
// Regenerate object at 21: Yes
// Regenerate object at 4: Yes
// Regenerate object at 38: No
// Regenerate object at 7: Yes
// Regenerate object at 2: Yes
// Regenerate object at 43: Yes
// Regenerate object at 38: No
// Cache size: 50, Regenerated: 94%
//