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ParallelEnumerable.ThenByDescending<TSource, TKey> Method (OrderedParallelQuery<TSource>, Func<TSource, TKey>, IComparer<TKey>)

Performs in parallel a subsequent ordering of the elements in a sequence in descending order by using a specified comparer.

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

public static OrderedParallelQuery<TSource> ThenByDescending<TSource, TKey>(
	this OrderedParallelQuery<TSource> source,
	Func<TSource, TKey> keySelector,
	IComparer<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.OrderedParallelQuery<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.IComparer<TKey>

An IComparer{TKey} to compare keys.

Return Value

Type: System.Linq.OrderedParallelQuery<TSource>
A sequence whose elements are sorted descending according to a key.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type OrderedParallelQuery<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
ArgumentNullException

source or keySelector is a null reference (Nothing in Visual Basic).

OperationCanceledException

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

AggregateException

One or more exceptions occurred during the evaluation of the query.

In contrast to the sequential implementation, this is not a stable sort. See the remarks for OrderBy for an approach to implementing a stable sort.

.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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