A couple of weeks ago, Jason Whittington (a fellow instructor at Developmentor) and I were doing a talk on asynchronous programming and we started with a very simple example of the APM -- using two loops to create and then consume the IAsyncResult work:

static void TwoLoopMain(string[] args)
{
   Queue<IAsyncResult> ars = new Queue<IAsyncResult>();
   Func<int,int,int> mathProc = Multiply;

   for (int i = 1; i <= 20; i++)
   {
      for (int j = 1; j <= 20; j++)
         ars.Enqueue(mathProc.BeginInvoke(i, j, null, null));
   }
   for (int i = 1; i <= 20; i++)
   {
      for (int j = 1; j <= 20; j++)
      {
         int result = mathProc.EndInvoke(ars.Dequeue());
         Console.SetCursorPosition(i * 3, j);
         Console.Write(result);
     }
  }
}

We had already presented a talk on LINQ earlier in the week and so I thought we might be able to do the above in a single expression with LINQ - kind of a challenge .. here's what we came up with:

static void LinqTest()
{
   Func<int,int,int> mathProc = Multiply;

   (from i in Enumerable.Range(1, 20)
    from j in Enumerable.Range(1, 20)
    select new { i, j, ar = mathProc.BeginInvoke(i, j, null, null) })
      .ToList()
      .ForEach(e => {
        int result = mathProc.EndInvoke(e.ar);
        Console.SetCursorPosition(e.i * 3, e.j);
        Console.Write(result);
     });
}

It's not easily readable (and so I wouldn't promote this for production code), but it's way cool and an example of how LINQ (and functional programming in general) is really changing the way programmers think about code.. just freaking cool..