ElementAtOrDefault(TSource) Method

Queryable.ElementAtOrDefault(Of TSource) Method (IQueryable(Of TSource), Int32)


Returns the element at a specified index in a sequence or a default value if the index is out of range.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

Public Shared Function ElementAtOrDefault(Of TSource) (
	source As IQueryable(Of TSource),
	index As Integer
) As TSource


Type: System.Linq.IQueryable(Of TSource)

An IQueryable(Of T) to return an element from.

Type: System.Int32

The zero-based index of the element to retrieve.

Return Value

Type: TSource

default(TSource) if index is outside the bounds of source; otherwise, the element at the specified position in source.

Type Parameters


The type of the elements of source.

Exception Condition

source is null.

The ElementAtOrDefault(Of TSource)(IQueryable(Of TSource), Int32) method generates a MethodCallExpression that represents calling ElementAtOrDefault(Of TSource)(IQueryable(Of TSource), Int32) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute(Of TResult)(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling ElementAtOrDefault(Of TSource)(IQueryable(Of TSource), Int32) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the item at position index in source, or default(TSource) if index is outside the bounds of source.

The following code example demonstrates how to use ElementAtOrDefault(Of TSource)(IQueryable(Of TSource), Int32). This example uses a value for index that is outside the bounds of the source sequence.

Dim names() As String = {"Hartono, Tommy", "Adams, Terry", _
                   "Andersen, Henriette Thaulow", _
                   "Hedlund, Magnus", "Ito, Shu"}

Dim index As Integer = 20

Dim name As String = names.AsQueryable().ElementAtOrDefault(index)

MsgBox(String.Format("The name at index {0} is '{1}'.", _
    index, IIf(String.IsNullOrEmpty(name), "[NONE AT THIS INDEX]", name)))

' This code produces the following output:
' The name at index 20 is '[NONE AT THIS INDEX]'.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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