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MSDN Library

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

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

Namespace:  System.Linq
Assemblies:   System.Linq.Parallel (in System.Linq.Parallel.dll)
  System.Core (in System.Core.dll)

<ExtensionAttribute> _
Public Shared Function Aggregate(Of TSource, TAccumulate, TResult) ( _
	source As ParallelQuery(Of TSource), _
	seed As TAccumulate, _
	updateAccumulatorFunc As Func(Of TAccumulate, TSource, TAccumulate), _
	combineAccumulatorsFunc As Func(Of TAccumulate, TAccumulate, TAccumulate), _
	resultSelector As Func(Of TAccumulate, TResult) _
) As TResult

Type Parameters


The type of the elements of source.


The type of the accumulator value.


The type of the resulting value.


Type: System.Linq.ParallelQuery(Of TSource)

A sequence to aggregate over.

Type: TAccumulate

The initial accumulator value.

Type: System.Func(Of TAccumulate, TSource, TAccumulate)

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

Type: System.Func(Of TAccumulate, TAccumulate, TAccumulate)

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

Type: System.Func(Of TAccumulate, TResult)

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

Return Value

Type: TResult
The transformed final accumulator value.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type ParallelQuery(Of 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).


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.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

.NET for Windows Phone apps

Supported in: Windows Phone 8.1

Portable Class Library

Supported in: Portable Class Library
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