public static GenerationUpdater GetUpdater(string groupKey)
{
if (groupKey.IsNullOrEmpty())
throw new ArgumentNullException("generationKey");
var updater = byGroupKey[groupKey] as GenerationUpdater;
if (updater == null)
{
var locked = Hashtable.Synchronized(byGroupKey);
updater = new GenerationUpdater(groupKey);
byGroupKey[groupKey] = byGroupKey[groupKey] ?? updater;
}
return updater;
}