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ParallelEnumerable.Select<TSource, TResult> Method (ParallelQuery<TSource>, Func<TSource, Int32, TResult>)

.NET Framework (current version)

Projects in parallel each element of a sequence into a new form by incorporating the element's index.

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

public static ParallelQuery<TResult> Select<TSource, TResult>(
	this ParallelQuery<TSource> source,
	Func<TSource, int, TResult> selector


Type: System.Linq.ParallelQuery<TSource>

A sequence of values to invoke a transform function on.

Type: System.Func<TSource, Int32, TResult>

A transform function to apply to each element.

Return Value

Type: System.Linq.ParallelQuery<TResult>

A sequence whose elements are the result of invoking the transform function on each element of source, based on the index supplied to selector.

Type Parameters


The type of the elements of source.


The type of elements resturned by selector.

Exception Condition

source or selector is a null reference (Nothing in Visual Basic).


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


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


More than MaxValue elements are enumerated by the query. This condition might occur in streaming scenarios.

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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