yield return in C# 4

OK, so I've been watching pluralsight videos lately and you would not believe how much they seem to love this "yield return" in C# 4.0.  Let's take a look at it in a small implementation.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            var numbers = new List<int>()
            {
                1,
                5,
                10,
                15,
                20,
                25
            };

            foreach (var number in GetLargeNumbers(numbers))
            {
                Console.WriteLine(number);
            }

            Console.Read();
        }

        static IEnumerable<int> GetLargeNumbers(IEnumerable<int> numbers)
        {
            foreach (var number in numbers)
            {
                if (number > 10)
                {
                    yield return number;
                }
            }
        }
    }
}

You can see that it saves some code.  For one, I don't need to build an enumerable and then return it at the end, I can just put a yield return and C# now builds it on the fly.  It kinda violates the O in SOLID to me, but that's not what its' value is.  It's value is that it only executes the code as it's needed.  This means that the numbers in the list are being evaluated each loop in the Main method, rather than all at once and then looped through.

I could show you changes to this program to test it, but I'll leave that for you.  Instead, I'll show you the really sexy part of this.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var number in GetRandomNumbers().Take(10))
            {
                Console.WriteLine(number);
            }

            Console.Read();
        }

        static IEnumerable<int> GetRandomNumbers()
        {
            var random = new Random();
            while (true)
            {
                yield return random.Next(30);
            }
        }
    }
}

Since yield return only executes as needed, we can deal with enormously large data-sets, even infinite, by only working on small pieces of them at a time.  In the example above, I create an infinite loop, that only executes for the number of random numbers I choose to Take (in this case 10).    Try it out, notice that it doesn't stack overflow on you!  Neat stuff.  I could get to like this yield return thing.