How would you implement the IEnumerator interface?

Question

I have a class that map objects to objects, but unlike dictionary it maps them both ways. I am now trying to implement a custom IEnumerator interface that iterates through t

Answer 1

First, don't make your collection object implement IEnumerator<>. This leads to bugs. (Consider the situation where two threads are iterating over the same collection).

Implementing an enumerator correctly turns out to be non-trivial, so C# 2.0 added special language support for doing it, based on the 'yield return' statement.

Raymond Chen's recent series of blog posts ("The implementation of iterators in C# and its consequences") is a good place to get up to speed.

• Part 1: https://web.archive.org/web/20081216071723/http://blogs.msdn.com/oldnewthing/archive/2008/08/12/8849519.aspx
• Part 2: https://web.archive.org/web/20080907004812/http://blogs.msdn.com/oldnewthing/archive/2008/08/13/8854601.aspx
• Part 3: https://web.archive.org/web/20080824210655/http://blogs.msdn.com/oldnewthing/archive/2008/08/14/8862242.aspx
• Part 4: https://web.archive.org/web/20090207130506/http://blogs.msdn.com/oldnewthing/archive/2008/08/15/8868267.aspx