/
GroupJoin.cs
65 lines (55 loc) · 2.75 KB
/
GroupJoin.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
namespace System.Linq
{
public static partial class Enumerable
{
public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(this IEnumerable<TOuter> outer, IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector, Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<TInner>, TResult> resultSelector) =>
GroupJoin(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer: null);
public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(this IEnumerable<TOuter> outer, IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector, Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<TInner>, TResult> resultSelector, IEqualityComparer<TKey>? comparer)
{
if (outer == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.outer);
}
if (inner == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.inner);
}
if (outerKeySelector == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.outerKeySelector);
}
if (innerKeySelector == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.innerKeySelector);
}
if (resultSelector == null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.resultSelector);
}
if (IsEmptyArray(outer))
{
return [];
}
return GroupJoinIterator(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer);
}
private static IEnumerable<TResult> GroupJoinIterator<TOuter, TInner, TKey, TResult>(IEnumerable<TOuter> outer, IEnumerable<TInner> inner, Func<TOuter, TKey> outerKeySelector, Func<TInner, TKey> innerKeySelector, Func<TOuter, IEnumerable<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);
do
{
TOuter item = e.Current;
yield return resultSelector(item, lookup[outerKeySelector(item)]);
}
while (e.MoveNext());
}
}
}
}
}