Enumerable.Last 方法

定義

命名空間:
System.Linq
組件:
System.Linq.dll, System.Core.dll, netstandard.dll

傳回序列的最後一個項目。Returns the last element of a sequence.

多載

Last<TSource>(IEnumerable<TSource>)

傳回序列的最後一個項目。Returns the last element of a sequence.
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

傳回序列中符合指定之條件的最後一個元素。Returns the last element of a sequence that satisfies a specified condition.

Last<TSource>(IEnumerable<TSource>)

傳回序列的最後一個項目。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

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IEnumerable<TSource>

要傳回最後一個項目的 IEnumerable<T>。An IEnumerable<T> to return the last element of.

傳回

TSource

位於來源序列中最後一個位置的值。The value at the last position in the source sequence.

例外狀況

ArgumentNullException

source 為 null。source is null.

InvalidOperationException

來源序列為空。The source sequence is empty.

範例

下列程式碼範例示範如何使用 Last<TSource>(IEnumerable<TSource>) 來傳回陣列的最後一個元素。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.
MsgBox(last)

' This code produces the following output:
'
' 19

備註

如果 source 未包含任何元素，則 Last<TSource>(IEnumerable<TSource>) 方法會擲回例外狀況。The Last<TSource>(IEnumerable<TSource>) method throws an exception if source contains no elements. 當來源序列是空的時，若要改為傳回預設值，請使用 LastOrDefault 方法。To instead return a default value when the source sequence is empty, use the LastOrDefault method.

Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

傳回序列中符合指定之條件的最後一個元素。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

類型參數

TSource

source 項目的類型。The type of the elements of source.

參數

source
IEnumerable<TSource>

傳回項目的 IEnumerable<T>。An IEnumerable<T> to return an element from.

predicate
Func<TSource,Boolean>

用來測試每個項目是否符合條件的函式。A function to test each element for a condition.

傳回

TSource

序列中通過指定之述詞函式所做測試的最後一個項目。The last element in the sequence that passes the test in the specified predicate function.

例外狀況

ArgumentNullException

source 或 predicate 為 null。source or predicate is null.

InvalidOperationException

沒有任何項目符合 predicate 的條件。No element satisfies the condition in predicate.

-或--or- 來源序列為空。The source sequence is empty.

範例

下列程式碼範例示範如何使用 Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 來傳回符合條件之陣列的最後一個元素。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.
MsgBox(last)

' This code produces the following output:
'
' 87

備註

如果在 source 中找不到相符的元素，則 Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) 方法會擲回例外狀況。The Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) method throws an exception if no matching element is found in source. 若要在找不到相符的元素時，改為傳回預設值，請使用 LastOrDefault 方法。To instead return a default value when no matching element is found, use the LastOrDefault method.

適用於