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ParallelEnumerable.Aggregate<TSource, TAccumulate, TResult> Method (ParallelQuery<TSource>, TAccumulate, Func<TAccumulate, TSource, TAccumulate>, Func<TAccumulate, TAccumulate, TAccumulate>, Func<TAccumulate, TResult>)

.NET Framework (current version)

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Applies in parallel an accumulator function over a sequence. This overload is not available in the sequential implementation.

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

public static TResult Aggregate<TSource, TAccumulate, TResult>(
	this ParallelQuery<TSource> source,
	TAccumulate seed,
	Func<TAccumulate, TSource, TAccumulate> updateAccumulatorFunc,
	Func<TAccumulate, TAccumulate, TAccumulate> combineAccumulatorsFunc,
	Func<TAccumulate, TResult> resultSelector


Type: System.Linq.ParallelQuery<TSource>

A sequence to aggregate over.

Type: TAccumulate

The initial accumulator value.

Type: System.Func<TAccumulate, TSource, TAccumulate>

An accumulator function to be invoked on each element in a partition.

Type: System.Func<TAccumulate, TAccumulate, TAccumulate>

An accumulator function to be invoked on the yielded accumulator result from each partition.

Type: System.Func<TAccumulate, TResult>

A function to transform the final accumulator value into the result value.

Return Value

Type: TResult

The transformed final accumulator value.

Type Parameters


The type of the elements of source.


The type of the accumulator value.


The type of the resulting value.

Exception Condition

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


source or updateAccumulatorFunc or combineAccumulatorsFunc or resultSelector is a null reference (Nothing in Visual Basic).


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


source contains no elements.

This overload is specific to processing a parallelized query. A parallelized query may partition the data source sequence into several sub-sequences (partitions). The updateAccumulatorFunc is invoked on each element within partitions. Each partition then yields a single accumulated result. The combineAccumulatorsFunc is then invoked on the results of each partition to yield a single element. This element is then transformed by the resultSelector function.

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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