ParallelEnumerable.FirstOrDefault Method

Definition

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>)

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

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.

Remarks

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

See also

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.

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

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

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

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

Applies to