public async Task <bool> MoveNext(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
if (_groupsEnumerator == null)
{
var groups = new Dictionary <TKey, Grouping <TKey, TElement> >();
using (var sourceEnumerator = _groupByAsyncEnumerable._source.GetEnumerator())
{
while (await sourceEnumerator.MoveNext(cancellationToken))
{
var key = _groupByAsyncEnumerable._keySelector(sourceEnumerator.Current);
var element = _groupByAsyncEnumerable._elementSelector(sourceEnumerator.Current);
Grouping <TKey, TElement> grouping;
if (!groups.TryGetValue(key, out grouping))
{
groups.Add(key, grouping = new Grouping <TKey, TElement>(key));
}
grouping.Add(element);
}
}
_groupsEnumerator = groups.Values.GetEnumerator();
}
return(_groupsEnumerator.MoveNext());
}
public async Task <bool> MoveNext(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
if (_sourceEnumerator == null)
{
_sourceEnumerator = _groupByAsyncEnumerable._source.GetEnumerator();
_hasNext = await _sourceEnumerator.MoveNext(cancellationToken);
}
if (_hasNext)
{
var currentKey = _groupByAsyncEnumerable._keySelector(_sourceEnumerator.Current);
var element = _groupByAsyncEnumerable._elementSelector(_sourceEnumerator.Current);
var grouping = new Grouping <TKey, TElement>(currentKey)
{
element
};
while (true)
{
_hasNext = await _sourceEnumerator.MoveNext(cancellationToken);
if (!_hasNext)
{
break;
}
if (!_comparer.Equals(
currentKey,
_groupByAsyncEnumerable._keySelector(_sourceEnumerator.Current)))
{
break;
}
grouping.Add(_groupByAsyncEnumerable._elementSelector(_sourceEnumerator.Current));
}
Current = grouping;
return(true);
}
return(false);
}