Item Property

ReadOnlyCollection.Item Property

Gets the element at the specified index.

Namespace: System.Collections.ObjectModel
Assembly: mscorlib (in mscorlib.dll)

Public ReadOnly Default Property Item ( _
	index As Integer _
) As T
Dim instance As ReadOnlyCollection(Of T)
Dim index As Integer
Dim value As T

value = instance(index)

/** @property */
public T get_Item (int index)

Not applicable.



The zero-based index of the element to get.

Property Value

The element at the specified index.

Exception typeCondition


index is less than zero.


index is equal to or greater than Count.

This property provides the ability to access a specific element in the collection by using the following C# syntax: myCollection[index] (myCollection(index) in Visual Basic).

The C# language uses the this keyword to define the indexers instead of implementing the Item property. Visual Basic implements Item as a default property, which provides the same indexing functionality.

Retrieving the value of this property is an O(1) operation.

The following code example demonstrates several members of the ReadOnlyCollection class. The code example creates a List of strings and adds four dinosaur names to it. The code example then wraps the list in a ReadOnlyCollection.

After demonstrating the Count, Contains, Item, and System.Collections.IList.IndexOf members, the code example shows that the ReadOnlyCollection is just a wrapper for the original List by adding a new item to the List and displaying the contents of the ReadOnlyCollection.

Finally, the code example creates an array larger than the collection and uses the CopyTo method to insert the elements of the collection into the middle of the array.

Imports System
Imports System.Collections.Generic
Imports System.Collections.ObjectModel

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)


        Dim readOnlyDinosaurs As _
            New ReadOnlyCollection(Of String)(dinosaurs)

        For Each dinosaur As String In readOnlyDinosaurs

        Console.WriteLine(vbLf & "Count: {0}", _

        Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _

        Console.WriteLine(vbLf & _
            "readOnlyDinosaurs(3): {0}", readOnlyDinosaurs(3))

        Console.WriteLine(vbLf & "IndexOf(""Compsognathus""): {0}", _

        Console.WriteLine(vbLf & "Insert into the wrapped List:")
        Console.WriteLine("Insert(2, ""Oviraptor"")")
        dinosaurs.Insert(2, "Oviraptor")

        For Each dinosaur As String In readOnlyDinosaurs

        Dim dinoArray(readOnlyDinosaurs.Count + 1) As String
        readOnlyDinosaurs.CopyTo(dinoArray, 1)

        Console.WriteLine(vbLf & "Copied array has {0} elements:", _
        For Each dinosaur As String In dinoArray
            Console.WriteLine("""{0}""", dinosaur)

   End Sub
End Class

' This code example produces the following output:
'Count: 4
'Contains("Deinonychus"): True
'readOnlyDinosaurs(3): Compsognathus
'IndexOf("Compsognathus"): 3
'Insert into the wrapped List:
'Insert(2, "Oviraptor")
'Copied array has 7 elements:

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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