Queryable.ElementAt(Of TSource) Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Returns the element at a specified index in a sequence.
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function ElementAt(Of TSource) ( _ source As IQueryable(Of TSource), _ index As Integer _ ) As TSource
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
- Type: System.Linq.IQueryable(Of TSource)
An IQueryable(Of T) to return an element from.
- index
- Type: System.Int32
The zero-based index of the element to retrieve.
Return Value
Type: TSourceThe element at the specified position in source.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable(Of TSource). When you use instance method syntax to call this method, omit the first parameter.| Exception | Condition |
|---|---|
| ArgumentNullException | source is Nothing. |
| ArgumentOutOfRangeException | index is less than zero. |
The ElementAt(Of TSource)(IQueryable(Of TSource), Int32) method generates a MethodCallExpression that represents calling ElementAt(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 ElementAt(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.
The following code example demonstrates how to use ElementAt(Of TSource)(IQueryable(Of TSource), Int32) to return an element at a specific position in a sequence.
Dim names() As String = {"Hartono, Tommy", "Adams, Terry", _
"Andersen, Henriette Thaulow", _
"Hedlund, Magnus", "Ito, Shu"}
Dim rand As New Random(DateTime.Now.Millisecond)
Dim name As String = _
names.AsQueryable().ElementAt(rand.Next(0, names.Length))
outputBlock.Text &= String.Format("The name chosen at random is '{0}'.", _
name) & vbCrLf
' This code produces the following sample output.
' Yours may be different due to the use of Random.
'
' The name chosen at random is 'Ito, Shu'.