And the award goes to...

The award for most... let's call it "innovative"... use of a C# Hashtable and an AsyncResult goes to:

private Hashtable _asyncResultToStudyUidMap = new Hashtable();


... later ...

IAsyncResult asyncResult = 
 _services.OrderService.BeginGetOrderForStudyPartially(
 orderId, studyId, orderPropertyArray, new 
 AsyncCallback(RequestOrderInfoCompleted), null);

_asyncResultToStudyUidMap[asyncResult] = studyUid;


... later ...

string studyUid = (string) _asyncResultToStudyUidMap[asyncResult];

if (studyUid != null)
{
 _cachedDictationInfos[studyUid] = dictationInfo;
 _asyncResultToStudyUidMap.Remove(asyncResult);
}

In case you're wondering, yes, we really are using the AsyncResult as the key to the Hashtable.

(Software development)