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MSDN Library

ParallelEnumerable.ForAll(TSource) Method

Invokes in parallel the specified action for each element in the source.

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

static member ForAll : 
        source:ParallelQuery<'TSource> * 
        action:Action<'TSource> -> unit

Type Parameters


The type of elements of source.


Type: System.Linq.ParallelQuery(TSource)

The ParallelQuery(TSource) whose elements will be processed by action.

Type: System.Action(TSource)

An Action to invoke on each element.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type ParallelQuery(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 action is a null reference (Nothing in Visual Basic).


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

This is an efficient way to process the output from a parallelized query because it does not require a merge step at the end. For more information, see Merge Options in PLINQ or Order Preservation in PLINQ. Because this method produces a side-effect, it can be used to observe the actual order of execution in a parallel query.

.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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