private static IEnumerable <TResult> JoinIterator <TOuter, TInner, TKey, TResult>(IEnumerable <TOuter> outer, IEnumerable <TInner> inner, Func <TOuter, TKey> outerKeySelector, Func <TInner, TKey> innerKeySelector, Func <TOuter, TInner, TResult> resultSelector, IEqualityComparer <TKey> comparer)
{
using (IEnumerator <TOuter> e = outer.GetEnumerator())
{
if (e.MoveNext())
{
Lookup <TKey, TInner> lookup = Lookup <TKey, TInner> .CreateForJoin(inner, innerKeySelector, comparer);
if (lookup.Count != 0)
{
do
{
TOuter item = e.Current;
Grouping <TKey, TInner> g = lookup.GetGrouping(outerKeySelector(item), false);
if (g != null)
{
int count = g.count;
TInner[] elements = g.elements;
for (int i = 0; i != count; ++i)
{
yield return(resultSelector(item, elements[i]));
}
}
} while (e.MoveNext());
}
}
}
}
internal static Lookup <TKey, TElement> Create(IEnumerable <TElement> source, Func <TElement, TKey> keySelector, IEqualityComparer <TKey> comparer)
{
Debug.Assert(source != null);
Debug.Assert(keySelector != null);
Lookup <TKey, TElement> lookup = new Lookup <TKey, TElement>(comparer);
foreach (TElement item in source)
{
lookup.GetGrouping(keySelector(item), create: true).Add(item);
}
return(lookup);
}
internal static Lookup <TKey, TElement> CreateForJoin(IEnumerable <TElement> source, Func <TElement, TKey> keySelector, IEqualityComparer <TKey> comparer)
{
Lookup <TKey, TElement> lookup = new Lookup <TKey, TElement>(comparer);
foreach (TElement local in source)
{
TKey key = keySelector(local);
if (key != null)
{
lookup.GetGrouping(key, true).Add(local);
}
}
return(lookup);
}
internal static Lookup <TKey, TElement> Create <TSource>(IEnumerable <TSource> source, Func <TSource, TKey> keySelector, Func <TSource, TElement> elementSelector, IEqualityComparer <TKey> comparer)
{
if (source == null)
{
throw Error.ArgumentNull("source");
}
if (keySelector == null)
{
throw Error.ArgumentNull("keySelector");
}
if (elementSelector == null)
{
throw Error.ArgumentNull("elementSelector");
}
Lookup <TKey, TElement> lookup = new Lookup <TKey, TElement>(comparer);
foreach (TSource local in source)
{
lookup.GetGrouping(keySelector(local), true).Add(elementSelector(local));
}
return(lookup);
}
