{"id":21223,"date":"2008-08-15T10:00:00","date_gmt":"2008-08-15T10:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2008\/08\/15\/the-implementation-of-iterators-in-c-and-its-consequences-part-4\/"},"modified":"2008-08-15T10:00:00","modified_gmt":"2008-08-15T10:00:00","slug":"the-implementation-of-iterators-in-c-and-its-consequences-part-4","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20080815-00\/?p=21223","title":{"rendered":"The implementation of iterators in C# and its consequences (part 4)"},"content":{"rendered":"

You can breathe a sigh of relief. Our long national nightmare is over<\/a>: this is the end of CLR Week 2008<\/a>. We wind down with a look back at iterators.<\/p>\n

Michael Entin<\/a> points out that you can use C# iterators to make asynchronous code easier to write<\/a>. You can use C# iterators for more than simply iterating. <\/p>\n

The automatic conversion of straight line code into a state machine is handy when you want an easy way to write, well, a state machine. It’s one of those things that’s blindingly obvious once you look at it the right way. <\/p>\n

The transformation that the yield return<\/code> statement induces on your function turns it from a boring function into an implicit state machine: When you execute a yield return<\/code>, execution of your function is suspended until somebody asks your iterator the next item, at which point execution resumes at the statement after the yield return<\/code>. This is exactly what you want when breaking a synchronous function into asynchronous pieces: Each time you would normally block on an operation, you instead perform a yield return<\/code>, and when the operation completes, you call the MoveNext<\/code> method, which resumes execution of the function until the next time it needs to wait for something and performs a yield return<\/code>. <\/p>\n

It’s so simple it’s magic. <\/p>\n

Additional iterator-related reading: <\/p>\n