public static IEnumerable <TGroup> GroupByGeneric <T, TKey, TValue, TGroupState, TGroup>(
this IEnumerable <KeyValuePair <TKey, TValue> > source,
ICollector <KeyValuePair <TKey, TValue>, TGroupState, TGroup> collector
)
{
var groups = new Dictionary <TKey, TGroupState>();
foreach (var item in source)
{
if (!groups.TryGetValue(item.Key, out var group))
{
groups[item.Key] = collector.Add(group, item);
}
else
{
groups.Add(item.Key, collector.Create(item));
}
}
foreach (var kv in groups)
{
yield return(collector.Complete(kv.Value));
}
}
