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

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 Parameters


The type of elements of source.


The type of the intermediate elements collected by collectionSelector.


The type of elements in the result sequence.


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.

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).


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.

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.