Collection.Item Property
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Default Property Item ( _ index As Integer _ ) As T 'Usage Dim instance As Collection(Of T) Dim index As Integer Dim value As T value = instance(index) instance(index) = value
/** @property */ public final T get_Item (int index) /** @property */ public final void set_Item (int index, T value)
Not applicable.
Parameters
- index
The zero-based index of the element to get or set.
Property Value
The element at the specified index.| Exception type | Condition |
|---|---|
| index is less than zero. -or- index is equal to or greater than Count. |
Collection accepts a null reference (Nothing in Visual Basic) as a valid value for reference types and allows duplicate elements.
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[index].
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; setting the property is also an O(1) operation.
Notes to Inheritors: Derived classes can override SetItem to change the behavior of setting this property.The following code example demonstrates many of the properties and methods of Collection. The code example creates a collection of strings, uses the Add method to add several strings, displays the Count, and lists the strings. The example uses the IndexOf method to find the index of a string and the Contains method to determine whether a string is in the collection. The example inserts a string using the Insert method and retrieves and sets strings using the default Item property (the indexer in C#). The example removes strings by string identity using the Remove method and by index using the RemoveAt method. Finally, the Clear method is used to clear all strings from the collection.
Imports System Imports System.Collections.Generic Imports System.Collections.ObjectModel Public Class Demo Public Shared Sub Main() Dim dinosaurs As New Collection(Of String) dinosaurs.Add("Psitticosaurus") dinosaurs.Add("Caudipteryx") dinosaurs.Add("Compsognathus") dinosaurs.Add("Muttaburrasaurus") Console.WriteLine("{0} dinosaurs:", dinosaurs.Count) Display(dinosaurs) Console.WriteLine(vbLf & "IndexOf(""Muttaburrasaurus""): {0}", _ dinosaurs.IndexOf("Muttaburrasaurus")) Console.WriteLine(vbLf & "Contains(""Caudipteryx""): {0}", _ dinosaurs.Contains("Caudipteryx")) Console.WriteLine(vbLf & "Insert(2, ""Nanotyrannus"")") dinosaurs.Insert(2, "Nanotyrannus") Display(dinosaurs) Console.WriteLine(vbLf & "dinosaurs(2): {0}", dinosaurs(2)) Console.WriteLine(vbLf & "dinosaurs(2) = ""Microraptor""") dinosaurs(2) = "Microraptor" Display(dinosaurs) Console.WriteLine(vbLf & "Remove(""Microraptor"")") dinosaurs.Remove("Microraptor") Display(dinosaurs) Console.WriteLine(vbLf & "RemoveAt(0)") dinosaurs.RemoveAt(0) Display(dinosaurs) Console.WriteLine(vbLf & "dinosaurs.Clear()") dinosaurs.Clear() Console.WriteLine("Count: {0}", dinosaurs.Count) End Sub Private Shared Sub Display(ByVal cs As Collection(Of String)) Console.WriteLine() For Each item As String In cs Console.WriteLine(item) Next item End Sub End Class ' This code example produces the following output: ' '4 dinosaurs: ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'IndexOf("Muttaburrasaurus"): 3 ' 'Contains("Caudipteryx"): True ' 'Insert(2, "Nanotyrannus") ' 'Psitticosaurus 'Caudipteryx 'Nanotyrannus 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs(2): Nanotyrannus ' 'dinosaurs(2) = "Microraptor" ' 'Psitticosaurus 'Caudipteryx 'Microraptor 'Compsognathus 'Muttaburrasaurus ' 'Remove("Microraptor") ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'RemoveAt(0) ' 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs.Clear() 'Count: 0
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.