multiple iterators on non-generic class - correct 'idiom'?

[emma_middlebrook]

Hi

Another query relating to iterators.

The following seems to work but it's different from the examples I can
find on MSDN ...

I'm trying to retrofit iterators into a non-generic class - here's an
attempt to make a forward and reverse one, with forward being the
default ...

One thing I can't quite figure out is why my foreach works when
specifying the 'named' enumerators?! Normally IEnumerator needs to be
returned but, below, IEnumerable is returned from the yield-versions -
foreach still works. I also noticed that it doesn't seem to matter
whether the iterator function returns IEnumerable or IEnumerator.
What's going on?

class SortedHashtable : IEnumerable
{
...

public IEnumerator GetEnumerator()
{
return GetForwardOrderEnumerator().GetEnumerator();
}

public IEnumerable GetForwardOrderEnumerator()
{
ArrayList sortedKeys = new ArrayList(hashtable.Keys);
sortedKeys.Sort();

foreach (object o in sortedKeys)
{
yield return new DictionaryEntry(o, hashtable[o]);
}
}

public IEnumerable GetReverseOrderEnumerator()
{
ArrayList sortedKeys = new ArrayList(hashtable.Keys);
sortedKeys.Sort();
sortedKeys.Reverse();

foreach (object o in sortedKeys)
{
yield return new DictionaryEntry(o, hashtable[o]);
}
}
}
Cheers

Emma