ICollection - Get single value

Question

What is the best way to get a value from a ICollection? We know the Collection is empty apart from that.

Answer 1

The simplest way to do this is:

foreach(object o in collection) {
  return o;
}

But this isn't particularly efficient if it's actually a generic collection because IEnumerator implements IDisposable, so the compiler has to put in a try/finally, with a Dispose() call in the finally block.

If it's a non-generic collection, or you know the generic collection implements nothing in its Dispose() method, then the following can be used:

IEnumerator en = collection.GetEnumerator();
en.MoveNext();
return en.Current;

If you know if may implement IList, you can do this:

IList iList = collection as IList;
if (iList != null) {
  // Implements IList, so can use indexer
  return iList[0];
}
// Use the slower way
foreach (object o in collection) {
  return o;
}

Likewise, if it's likely it'll be of a certain type of your own definition that has some kind of indexed access, you can use the same technique.