"The anatomy of closures" blog post

Closure.cs

class Anon1
{
  private int second;

  // constructor
  public Anon1(int second) 
  {
    this.second = second;
  }

  public int Apply(int x)
  {
    return second * x;
  }
}

EvilIncarnate.cs

class EvilIncarnate
{
  // hold the reference forever
  private static PandorasBox boxOfSecrets;

  public int[] CalculateDeviations(int ages)
  {
    var dataTable = // query the database for average age
    boxOfSecrets = new PandorasBox();
    return boxOfSecrets.Map(ages, x => ((int)dataTable[0]) * x);
  }
}

Map.cs

public int[] Map(int[] original, Func<int, int> mapper) 
{
  var result = new int[original.Length];
  for (int i = 0; i < original.Length; i++)
    result[i] = mapper(original[i]);
  return result;
}

MapList.cs

var numbers = new[] { 1, 5, 3, 17 };
var squares = Map(numbers, x => x * x);
var halves = Map(numbers, x => x / 2);
var second = DateTime.Now.Second;
var aritrary = Map(numbers, x => second * x);

PandorasBox.cs

class PandorasBox
{
  private Func<int, int> captor;

  public int[] Map(int[] numbers, Func<int, int> functor)
  {
    captor = functor;
    // ...
  }
}