ParallelEnumerable.SelectMany<TSource, TCollection, TResult> Method (ParallelQuery<TSource>, Func<TSource, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>)

.NET Framework (current version)

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Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.

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

public static ParallelQuery<TResult> SelectMany<TSource, TCollection, TResult>(
	this ParallelQuery<TSource> source,
	Func<TSource, IEnumerable<TCollection>> collectionSelector,
	Func<TSource, TCollection, TResult> resultSelector


Type: System.Linq.ParallelQuery<TSource>

A sequence of values to project.

Type: System.Func<TSource, IEnumerable<TCollection>>

A transform function to apply to each source element; the second parameter of the function represents the index of the source element.

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

A function to create a result element from an element from the first sequence and a collection of matching elements from the second sequence.

Return Value

Type: System.Linq.ParallelQuery<TResult>

A sequence whose elements are the result of invoking the one-to-many transform function collectionSelector on each element of source based on the index supplied to collectionSelector, and then mapping each of those sequence elements and their corresponding source element to a result element.

Type Parameters


The type of the intermediate elements collected by collectionSelector.


The type of elements of source.


The type of elements in the result sequence.

Exception Condition

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


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


More than MaxValue elements are enumerated by the query.


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

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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