Enumerable.ElementAt<TSource>(IEnumerable<TSource>, Int32) 方法

定義

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

傳回位於序列中指定索引處的項目。Returns the element at a specified index in a sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource ElementAt(System::Collections::Generic::IEnumerable<TSource> ^ source, int index);
public static TSource ElementAt<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, int index);
static member ElementAt : seq<'Source> * int -> 'Source
<Extension()>
Public Function ElementAt(Of TSource) (source As IEnumerable(Of TSource), index As Integer) 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.

index
Int32

要擷取的項目之以零為起始索引。The zero-based index of the element to retrieve.

傳回

TSource

位於來源序列中指定位置的項目。The element at the specified position in the source sequence.

例外狀況

ArgumentNullException

source 為 null。source is null.

ArgumentOutOfRangeException

index 小於 0 或大於或等於 source 中的項目數目。index is less than 0 or greater than or equal to the number of elements in source.

範例

下列程式碼範例示範如何使用傳回 ElementAt 特定位置的元素。The following code example demonstrates how to use ElementAt to return an element at a specific position.

string[] names =
    { "Hartono, Tommy", "Adams, Terry", "Andersen, Henriette Thaulow",

        "Hedlund, Magnus", "Ito, Shu" };
Random random = new Random(DateTime.Now.Millisecond);

string name = names.ElementAt(random.Next(0, names.Length));

Console.WriteLine("The name chosen at random is '{0}'.", name);

/*
 This code produces the following sample output:

 The name chosen at random is 'Ito, Shu'.
*/

' Create an array of strings.
Dim names() As String =
{"Hartono, Tommy", "Adams, Terry", "Andersen, Henriette Thaulow", "Hedlund, Magnus", "Ito, Shu"}

Dim random As Random = New Random(DateTime.Now.Millisecond)

' Get a string at a random index within the array.
Dim name As String = names.ElementAt(random.Next(0, names.Length))

' Display the output.
Console.WriteLine($"The name chosen at random is {name}")

' This code produces the following output:
'
' The name chosen at random is Ito, Shu

備註

如果實作為的型別 source IList<T> ，則會使用該執行來取得指定之索引處的元素。If the type of source implements IList<T>, that implementation is used to obtain the element at the specified index. 否則，這個方法會取得指定的元素。Otherwise, this method obtains the specified element.

如果超出範圍，這個方法會擲回例外狀況 index 。This method throws an exception if index is out of range. 若要改為在指定的索引超出範圍時傳回預設值，請使用 ElementAtOrDefault 方法。To instead return a default value when the specified index is out of range, use the ElementAtOrDefault method.

適用於