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

Groups in parallel the elements of a sequence according to a specified key selector function and projects the elements for each group 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
)

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<TKey, TElement>.

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<TKey, TElement>.

Return Value

Type: System.Linq.ParallelQuery<IGrouping<TKey, TElement>>
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: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1
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