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)

Syntax

C++

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.

Exceptions

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.

Version Information

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