public static SimpleLookup <TKey, TElement> Create <TSource>(
IEnumerable <TSource> source,
Func <TSource, TKey> keySelector,
Func <TSource, TElement> elementSelector,
IEqualityComparer <TKey> comparer)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (keySelector == null)
{
throw new ArgumentNullException(nameof(keySelector));
}
if (elementSelector == null)
{
throw new ArgumentNullException(nameof(elementSelector));
}
var lookup = new SimpleLookup <TKey, TElement>(comparer);
foreach (var source1 in source)
{
lookup.GetGrouping(keySelector(source1), true).Add(elementSelector(source1));
}
return(lookup);
}
public static SimpleLookup <TKey, TElement> CreateForJoin(
IEnumerable <TElement> source,
Func <TElement, TKey> keySelector,
IEqualityComparer <TKey> comparer)
{
var lookup = new SimpleLookup <TKey, TElement>(comparer);
foreach (var element in source)
{
var key = keySelector(element);
if (key != null)
{
lookup.GetGrouping(key, true).Add(element);
}
}
return(lookup);
}