Cannot step into a method returning IEnumerable?

Question

I have a method that returns an IEnumerable like this..

public virtual IEnumerable ToPages(){
  // foreach logic
  yield return pages;

  // more         


        

Answer 1

As others have noted, the body of an iterator block is not executed until the iterator is actually moved. Just creating the iterator does nothing other than creating it. People often find this confusing.

If the design and implementation of iterator blocks interests you, here are some good articles on the subject:

Raymond Chen: (short introduction to the basic points)

http://blogs.msdn.com/b/oldnewthing/archive/2008/08/12/8849519.aspx

http://blogs.msdn.com/b/oldnewthing/archive/2008/08/13/8854601.aspx

http://blogs.msdn.com/b/oldnewthing/archive/2008/08/14/8862242.aspx

Jon Skeet: (long, in depth)

http://csharpindepth.com/Articles/Chapter6/IteratorBlockImplementation.aspx

Eric Lippert (me): (advanced scenarios and corner cases)

http://blogs.msdn.com/b/ericlippert/archive/tags/iterators/