Returns the element at a specified index in a sequence or a default value if the index is out of range.
(in System.Core.dll)
Visual Basic (Declaration)
<ExtensionAttribute> _
Public Shared Function ElementAtOrDefault(Of TSource) ( _
source As IEnumerable(Of TSource), _
index As Integer _
) As TSource
Dim source As IEnumerable(Of TSource)
Dim index As Integer
Dim returnValue As TSource
returnValue = source.ElementAtOrDefault(index)
public static TSource ElementAtOrDefault<TSource>(
this IEnumerable<TSource> source,
int index
)
[ExtensionAttribute]
public:
generic<typename TSource>
static TSource ElementAtOrDefault(
IEnumerable<TSource>^ source,
int index
)
JScript does not support generic types or methods.
Type Parameters
- TSource
The type of the elements of source.
Return Value
Type: TSource
default(TSource) if the index is outside the bounds of the source sequence; otherwise, the element at the specified position in the source sequence.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<(Of <(TSource>)>). When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).
| Exception | Condition |
|---|
| ArgumentNullException |
source is nullNothingnullptra null reference (Nothing in Visual Basic). |
If the type of source implements IList<(Of <(T>)>), that implementation is used to obtain the element at the specified index. Otherwise, this method obtains the specified element.
The default value for reference and nullable types is nullNothingnullptra null reference (Nothing in Visual Basic).
The following code example demonstrates how to use ElementAtOrDefault<(Of <(TSource>)>). This example uses an index that is outside the bounds of the array.
' Create an array of strings.
Dim names() As String = _
{"Hartono, Tommy", "Adams, Terry", "Andersen, Henriette Thaulow", "Hedlund, Magnus", "Ito, Shu"}
Dim index As Integer = 20
' Get a string at an index that is out of range in the array.
Dim name As String = names.ElementAtOrDefault(index)
Dim text As String = IIf(String.IsNullOrEmpty(name), "[THERE IS NO NAME AT THIS INDEX]", name)
' Display the output.
MsgBox("The name chosen at index " & index & " is " & text)
' This code produces the following output:
'
' The name chosen at index 20 is [THERE IS NO NAME AT THIS INDEX]
string[] names =
{ "Hartono, Tommy", "Adams, Terry", "Andersen, Henriette Thaulow",
"Hedlund, Magnus", "Ito, Shu" };
int index = 20;
string name = names.ElementAtOrDefault(index);
Console.WriteLine(
"The name chosen at index {0} is '{1}'.",
index,
String.IsNullOrEmpty(name) ? "<no name at this index>" : name);
/*
This code produces the following output:
The name chosen at index 20 is '<no name at this index>'.
*/
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5
.NET Compact Framework
Supported in: 3.5
XNA Framework
Supported in: 3.0
Reference