Enumerable.Last 方法
定义
返回序列的最后一个元素。Returns the last element of a sequence.
重载
| Last<TSource>(IEnumerable<TSource>) |
返回序列的最后一个元素。Returns the last element of a sequence. |
| Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) |
返回序列中满足指定条件的最后一个元素。Returns the last element of a sequence that satisfies a specified condition. |
Last<TSource>(IEnumerable<TSource>)
返回序列的最后一个元素。Returns the last element of a sequence.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static TSource Last(System::Collections::Generic::IEnumerable<TSource> ^ source);public static TSource Last<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);static member Last : seq<'Source> -> 'Source<Extension()>
Public Function Last(Of TSource) (source As IEnumerable(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
- IEnumerable<TSource>
要返回其最后一个元素的 IEnumerable<T>。An IEnumerable<T> to return the last element of.
返回
- TSource
源序列中最后位置处的值。The value at the last position in the source sequence.
例外
source 为 null。source is null.
源序列为空。The source sequence is empty.
示例
下面的代码示例演示如何使用 Last<TSource>(IEnumerable<TSource>) 返回数组的最后一个元素。The following code example demonstrates how to use Last<TSource>(IEnumerable<TSource>) to return the last element of an array.
int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54,
83, 23, 87, 67, 12, 19 };
int last = numbers.Last();
Console.WriteLine(last);
/*
This code produces the following output:
19
*/
' Create an array of integers.
Dim numbers() As Integer =
{9, 34, 65, 92, 87, 435, 3, 54, 83, 23, 87, 67, 12, 19}
' Get the last item in the array.
Dim last As Integer = numbers.Last()
' Display the result.
Console.WriteLine(last)
' This code produces the following output:
'
' 19
注解
Last<TSource>(IEnumerable<TSource>)如果 source 不包含任何元素，则该方法将引发异常。The Last<TSource>(IEnumerable<TSource>) method throws an exception if source contains no elements. 若要改为在源序列为空时返回默认值，请使用 LastOrDefault 方法。To instead return a default value when the source sequence is empty, use the LastOrDefault method.
适用于
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)
返回序列中满足指定条件的最后一个元素。Returns the last element of a sequence that satisfies a specified condition.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static TSource Last(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);public static TSource Last<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);static member Last : seq<'Source> * Func<'Source, bool> -> 'Source<Extension()>
Public Function Last(Of TSource) (source As IEnumerable(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
- IEnumerable<TSource>
要从中返回元素的 IEnumerable<T>。An IEnumerable<T> to return an element from.
返回
- TSource
序列中通过指定谓词函数中的测试的最后一个元素。The last element in the sequence that passes the test in the specified predicate function.
例外
source 或 predicate 为 null。source or predicate is null.
元素均不满足 predicate 中的条件。No element satisfies the condition in predicate.
- 或 --or- 源序列为空。The source sequence is empty.
示例
下面的代码示例演示如何使用 Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 返回数组中满足条件的最后一个元素。The following code example demonstrates how to use Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to return the last element of an array that satisfies a condition.
int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54,
83, 23, 87, 67, 12, 19 };
int last = numbers.Last(num => num > 80);
Console.WriteLine(last);
/*
This code produces the following output:
87
*/
' Create an array of integers.
Dim numbers() As Integer =
{9, 34, 65, 92, 87, 435, 3, 54, 83, 23, 87, 67, 12, 19}
' Get the last element in the array whose value is
' greater than 80.
Dim last As Integer = numbers.Last(Function(num) num > 80)
' Display the result.
Console.WriteLine(last)
' This code produces the following output:
'
' 87
注解
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)如果在中未找到匹配的元素，此方法将引发异常 source 。The Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) method throws an exception if no matching element is found in source. 如果未找到匹配的元素，则改为返回默认值时，请使用 LastOrDefault 方法。To instead return a default value when no matching element is found, use the LastOrDefault method.