ParallelEnumerable::ToLookup<TSource, TKey> Method (ParallelQuery<TSource>^, Func<TSource, TKey>^, IEqualityComparer<TKey>^)

.NET Framework (current version)
 

Creates an ILookup<TKey, TElement> from a ParallelQuery<TSource> according to a specified key selector function and key comparer.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

public:
generic<typename TSource, typename TKey>
[ExtensionAttribute]
static ILookup<TKey, TSource>^ ToLookup(
	ParallelQuery<TSource>^ source,
	Func<TSource, TKey>^ keySelector,
	IEqualityComparer<TKey>^ comparer
)

Parameters

source
Type: System.Linq::ParallelQuery<TSource>^

The sequence to create a ILookup<TKey, TElement> from.

keySelector
Type: System::Func<TSource, TKey>^

A function to extract a key from each element.

comparer
Type: System.Collections.Generic::IEqualityComparer<TKey>^

An IEqualityComparer<T> to compare keys.

Return Value

Type: System.Linq::ILookup<TKey, TSource>^

A ILookup<TKey, TElement> that contains keys and values.

Type Parameters

TSource

The type of elements of source.

TKey

The type of the key returned by keySelector.

Exception Condition
OperationCanceledException

The query was canceled with the token passed in through WithCancellation.

ArgumentNullException

source or keySelector or is a null reference (Nothing in Visual Basic).

AggregateException

One or more exceptions occurred during the evaluation of the query.

Universal Windows Platform
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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