ParallelEnumerable.FirstOrDefault Method

Definition

Namespace:

System.Linq

Assembly:

System.Linq.Parallel.dll

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

Overloads

FirstOrDefault<TSource>(ParallelQuery<TSource>)	Returns the first element of a parallel sequence, or a default value if the sequence contains no elements.
FirstOrDefault<TSource>(ParallelQuery<TSource>, Func<TSource,Boolean>)	Returns the first element of the parallel sequence that satisfies a condition or a default value if no such element is found.

FirstOrDefault<TSource>(ParallelQuery<TSource>)

Source:

ParallelEnumerable.cs

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

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource FirstOrDefault(System::Linq::ParallelQuery<TSource> ^ source);

public static TSource? FirstOrDefault<TSource> (this System.Linq.ParallelQuery<TSource> source);

static member FirstOrDefault : System.Linq.ParallelQuery<'Source> -> 'Source

<Extension()>
Public Function FirstOrDefault(Of TSource) (source As ParallelQuery(Of TSource)) As TSource

Type Parameters

TSource

The type of the elements of source.

Parameters

source

ParallelQuery<TSource>

The sequence to return the first element of.

Returns

TSource

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

Exceptions

OperationCanceledException

The query was canceled with the token passed in through WithCancellation<TSource>(ParallelQuery<TSource>, CancellationToken).

ArgumentNullException

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

AggregateException

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

Remarks

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

See also

• Parallel LINQ (PLINQ)

FirstOrDefault<TSource>(ParallelQuery<TSource>, Func<TSource,Boolean>)

Source:

ParallelEnumerable.cs

Returns the first element of the parallel sequence that satisfies a condition or a default value if no such element is found.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource FirstOrDefault(System::Linq::ParallelQuery<TSource> ^ source, Func<TSource, bool> ^ predicate);

public static TSource? FirstOrDefault<TSource> (this System.Linq.ParallelQuery<TSource> source, Func<TSource,bool> predicate);

static member FirstOrDefault : System.Linq.ParallelQuery<'Source> * Func<'Source, bool> -> 'Source

<Extension()>
Public Function FirstOrDefault(Of TSource) (source As ParallelQuery(Of TSource), predicate As Func(Of TSource, Boolean)) As TSource

Type Parameters

TSource

The type of the elements of source.

Parameters

source

ParallelQuery<TSource>

The sequence to return an element from.

predicate

Func<TSource,Boolean>

A function to test each element for a condition.

Returns

TSource

default(TSource) if source is empty or if no element passes the test specified by predicate; otherwise, the first element in source that passes the test specified by predicate.

Exceptions

OperationCanceledException

The query was canceled with the token passed in through WithCancellation<TSource>(ParallelQuery<TSource>, CancellationToken).

ArgumentNullException

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

AggregateException

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

Remarks

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

See also

• Parallel LINQ (PLINQ)