ParallelEnumerable.First 方法

定义

返回并行序列中的第一个元素。Returns the first element of a parallel sequence.

重载

First<TSource>(ParallelQuery<TSource>)

返回并行序列中的第一个元素。Returns the first element of a parallel sequence.

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

返回并行序列中满足指定条件的第一个元素。Returns the first element in a parallel sequence that satisfies a specified condition.

First<TSource>(ParallelQuery<TSource>)

返回并行序列中的第一个元素。Returns the first element of a parallel sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource First(System::Linq::ParallelQuery<TSource> ^ source);
public static TSource First<TSource> (this System.Linq.ParallelQuery<TSource> source);
static member First : System.Linq.ParallelQuery<'Source> -> 'Source
<Extension()>
Public Function First(Of TSource) (source As ParallelQuery(Of TSource)) As TSource

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
ParallelQuery<TSource>

要返回其第一个元素的序列。The sequence to return the first element of.

返回

TSource

返回指定序列中的第一个元素。The first element in the specified sequence.

例外

已使用通过 WithCancellation 传递的令牌取消了查询。The query was canceled with the token passed in through WithCancellation.

source 为 null 引用(在 Visual Basic 中为 Nothing)。source is a null reference (Nothing in Visual Basic).

评估查询期间发生一个或多个异常。One or more exceptions occurred during the evaluation of the query.

source 中不包含任何元素。source contains no elements.

注解

如果查询未排序,则第一个元素是不确定的。If the query is not ordered, then the first element is non-deterministic. 有关详细信息,请参阅 PLINQ 中的顺序保留For more information, see Order Preservation in PLINQ.

另请参阅

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

返回并行序列中满足指定条件的第一个元素。Returns the first element in a parallel sequence that satisfies a specified condition.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource First(System::Linq::ParallelQuery<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static TSource First<TSource> (this System.Linq.ParallelQuery<TSource> source, Func<TSource,bool> predicate);
static member First : System.Linq.ParallelQuery<'Source> * Func<'Source, bool> -> 'Source
<Extension()>
Public Function First(Of TSource) (source As ParallelQuery(Of TSource), predicate As Func(Of TSource, Boolean)) As TSource

类型参数

TSource

source 的元素类型。The type of the elements of source.

参数

source
ParallelQuery<TSource>

要从中返回元素的序列。The sequence to return an element from.

predicate
Func<TSource,Boolean>

用于测试每个元素是否满足条件的函数。A function to test each element for a condition.

返回

TSource

序列中通过指定谓词函数中的测试的第一个元素。The first element in the sequence that passes the test in the specified predicate function.

例外

已使用通过 WithCancellation 传递的令牌取消了查询。The query was canceled with the token passed in through WithCancellation.

sourcepredicate 为 null 引用(在 Visual Basic 中为 Nothing)。source or predicate is a null reference (Nothing in Visual Basic).

评估查询期间发生一个或多个异常。One or more exceptions occurred during the evaluation of the query.

source 中没有元素满足 predicate 中的条件。No element in source satisfies the condition in predicate.

注解

如果查询未排序,则第一个元素是不确定的。If the query is not ordered, then the first element is non-deterministic. 有关详细信息,请参阅 PLINQ 中的顺序保留For more information, see Order Preservation in PLINQ.

另请参阅

适用于