ndIterators.aspx">couple</a> of <a href="http://csharpindepth.com/Articles/Chapter6/IteratorBlockImplementation.aspx">articles</a> you can read if you want more background details... or read chapter 6 of C# in Depth (either edition). These give us deferred execution for free... but that can be a curse as well as a blessing, as we&#39;ll see in a minute.</p>  <p>At its heart, the implementation is going to look something like this:</p>  <div class="code"><span class="InlineComment">// Naive implementation</s