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Parallel.ForEach<TSource> Method (OrderablePartitioner<TSource>, Action<TSource, ParallelLoopState, Int64>)

Executes a foreach (For Each in Visual Basic) operation on a OrderablePartitioner<TSource> in which iterations may run in parallel and the state of the loop can be monitored and manipulated.

Namespace:  System.Threading.Tasks
Assembly:  mscorlib (in mscorlib.dll)

public static ParallelLoopResult ForEach<TSource>(
	OrderablePartitioner<TSource> source,
	Action<TSource, ParallelLoopState, long> body

Type Parameters


The type of the elements in source.


Type: System.Collections.Concurrent.OrderablePartitioner<TSource>

The orderable partitioner that contains the original data source.

Type: System.Action<TSource, ParallelLoopState, Int64>

The delegate that is invoked once per iteration.

Return Value

Type: System.Threading.Tasks.ParallelLoopResult
A structure that contains information about which portion of the loop completed.


The source argument is null.


The body argument is null.


The SupportsDynamicPartitions property in the source orderable partitioner returns false.


The KeysNormalized property in the source orderable partitioner returns false.


Any methods in the source orderable partitioner return null.

This overload is provided for scenarios where you want to override the default partitioning scheme. For example, small loop bodies might benefit from partitioning the range. The Parallel.ForEach method expects custom partitioners to support dynamic partitioning. For more information, see Custom Partitioners for PLINQ and TPL and How to: Implement Dynamic Partitions.

.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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