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

.NET Framework 4.6 and 4.5

Executes a foreach (For Each in Visual Basic) operation with 64-bit indexes on an IEnumerable 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>(
	IEnumerable<TSource> source,
	Action<TSource, ParallelLoopState, long> body


Type: System.Collections.Generic.IEnumerable<TSource>

An enumerable 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.

Type Parameters


The type of the data in the source.

Exception Condition

The source argument is null.


The body argument is null.


The exception that contains all the individual exceptions thrown on all threads.

The body delegate is invoked once for each element in the source enumerable. It is provided with the following parameters: the current element, a ParallelLoopState instance that may be used to break out of the loop prematurely, and the current element's index (Int64).

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
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