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ParallelEnumerable.FirstOrDefault<TSource> Method (ParallelQuery<TSource>)

.NET Framework (current version)

Returns the first element of a parallel sequence, or a default value if the sequence contains no elements.

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

public static TSource FirstOrDefault<TSource>(
	this ParallelQuery<TSource> source


Type: System.Linq.ParallelQuery<TSource>

The sequence to return the first element of.

Return Value

Type: TSource

default(TSource) if source is empty; otherwise, the first element in source.

Type Parameters


The type of the elements of source.

Exception Condition

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


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


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

If the query is not ordered, then the first element is non-deterministic. For more information, see Order Preservation in PLINQ.

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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