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

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 Parameters

TSource

The type of the elements of source.

Parameters

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.

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).

ExceptionCondition
OperationCanceledException

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

ArgumentNullException

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

AggregateException

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.

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1
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