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

Groups in parallel the elements of a sequence according to a specified key selector function and compares the keys by using a specified IComparer<T>.

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

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

Type Parameters

TSource

The type of elements of source.

TKey

The type of the key returned by keySelector>.

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.

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

An IComparer<T> to compare keys.

Return Value

Type: System.Linq.ParallelQuery<IGrouping<TKey, TSource>>
A sequence of groups that are sorted descending according to TKey.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type ParallelQuery<TSource>. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
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.

.NET Framework

Supported in: 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1

Windows Phone 8.1, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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