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

.NET Framework (current version)

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

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

Syntax

C++

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

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.

elementSelector: Type: System::Func<TSource, TElement>^
A transform function to produce a result element value from each element.

Return Value

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

A ILookup<TKey, TElement> that contains values of type TElement selected from the input sequence.

Type Parameters

TSource: The type of elements of source.

TKey: The type of the key returned by keySelector.

TElement: The type of the value returned by elementSelector.

Exceptions

Exception	Condition
OperationCanceledException	The query was canceled with the token passed in through WithCancellation.
ArgumentNullException	source or keySelector or elementSelector 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