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ParallelEnumerable.GroupBy<TSource, TKey, TElement> Method (ParallelQuery<TSource>, Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)

.NET Framework (current version)
 

Groups in parallel the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.

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

public static ParallelQuery<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
	this ParallelQuery<TSource> source,
	Func<TSource, TKey> keySelector,
	Func<TSource, TElement> elementSelector,
	IEqualityComparer<TKey> comparer
)

Parameters

source
Type: System.Linq.ParallelQuery<TSource>

An OrderedParallelQuery{TSource}that contains elements to sort.

keySelector
Type: System.Func<TSource, TKey>

A function to extract a key from an element.

elementSelector
Type: System.Func<TSource, TElement>

A function to map each source element to an element in an IGrouping.

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

An IComparer{TSource} to compare keys.

Return Value

Type: System.Linq.ParallelQuery<IGrouping<TKey, TElement>>

A sequence of groups that are sorted descending according to TKey.

Type Parameters

TSource

The type of elements of source.

TKey

The type of the key returned by keySelector.

TElement

The type of the elements in the IGrouping

Exception Condition
OperationCanceledException

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

ArgumentNullException

source or action 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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