assed the item, not the index. The tests involving the index are very similar.</p>  <h3>Let&#39;s implement it!</h3>  <p>With all the tests passing when running against the real LINQ to Objects, it&#39;s time to implement it in our production code. We&#39;re going to use <a href="http://msdn.microsoft.com/en-us/library/dscyy5s0.aspx">iterator blocks</a>, which were introduced in C# 2 to make it easier to implement IEnumerable&lt;T&gt;. I have a <a href="http://csharpindepth.com/Articles/Chapter11/StreamingA