Working with the Yield keyword in C#

I just started using a neat trick in C# when working with iterators: the yield keyword. This lets you easily return items as an IEnumerable without having to worry about state. It looks like this:

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

namespace WorkingWithYield
{
 class Program
 {
     static IEnumerable<string> GetIDs()
     {
         for (int i = 0; i < 10; i++)
         {
             Console.WriteLine("generating " + i);
             yield return i.ToString();
         }
     }

     static void Main(string[] args)
     {
         IEnumerable<string> IDs = GetIDs();

         foreach (string ID in IDs)
             Console.WriteLine("printing   " + ID);

         Console.Read();
     }
 }
}

Output:

generating 0 printing 0 generating 1 printing 1 generating 2 printing 2 generating 3 printing 3 generating 4 printing 4 generating 5 printing 5 generating 6 printing 6 generating 7 printing 7 generating 8 printing 8 generating 9 printing 9

As you can see, the system effectively pauses the loop when it returns an item to the foreach loop--the numbers are lazily generated when needed, not all at once before they are printed. When an IEnumerable works, this can be very handy. Neat stuff.