Collection.InsertItem Method
Assembly: mscorlib (in mscorlib.dll)
'Declaration Protected Overridable Sub InsertItem ( _ index As Integer, _ item As T _ ) 'Usage Dim index As Integer Dim item As T Me.InsertItem(index, item)
protected void InsertItem ( int index, T item )
protected function InsertItem ( index : int, item : T )
Not applicable.
Parameters
- index
The zero-based index at which item should be inserted.
- item
The object to insert. The value can be a null reference (Nothing in Visual Basic) for reference types.
| Exception type | Condition |
|---|---|
| index is less than zero. -or- index is greater than Count. |
The following code example shows how to derive a collection class from a constructed type of the Collection generic class, and how to override the protected InsertItem, RemoveItem, ClearItems, and SetItem methods to provide custom behavior for the Add, Insert, Remove, and Clear methods, and for setting the Item property.
The custom behavior provided by this example is a Changed notification event that is raised at the end of each of the protected methods. The Dinosaurs class inherits Collection<string> (Collection(Of String) in Visual Basic) and defines the Changed event, which uses a DinosaursChangedEventArgs class for the event information, and an enumeration to identify the kind of change.
The code example calls several properties and methods of Collection to demonstrate the custom event.
Imports System Imports System.Collections.Generic Imports System.Collections.ObjectModel Public Class Dinosaurs Inherits Collection(Of String) Public Event Changed As EventHandler(Of DinosaursChangedEventArgs) Protected Overrides Sub InsertItem( _ ByVal index As Integer, ByVal newItem As String) MyBase.InsertItem(index, newItem) RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _ ChangeType.Added, newItem, Nothing)) End Sub Protected Overrides Sub SetItem(ByVal index As Integer, _ ByVal newItem As String) Dim replaced As String = Items(index) MyBase.SetItem(index, newItem) RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _ ChangeType.Replaced, replaced, newItem)) End Sub Protected Overrides Sub RemoveItem(ByVal index As Integer) Dim removedItem As String = Items(index) MyBase.RemoveItem(index) RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _ ChangeType.Removed, removedItem, Nothing)) End Sub Protected Overrides Sub ClearItems() MyBase.ClearItems() RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _ ChangeType.Cleared, Nothing, Nothing)) End Sub End Class ' Event argument for the Changed event. ' Public Class DinosaursChangedEventArgs Inherits EventArgs Public ReadOnly ChangedItem As String Public ReadOnly ChangeType As ChangeType Public ReadOnly ReplacedWith As String Public Sub New(ByVal change As ChangeType, ByVal item As String, _ ByVal replacement As String) ChangeType = change ChangedItem = item ReplacedWith = replacement End Sub End Class Public Enum ChangeType Added Removed Replaced Cleared End Enum Public Class Demo Public Shared Sub Main() Dim dinosaurs As New Dinosaurs AddHandler dinosaurs.Changed, AddressOf ChangedHandler dinosaurs.Add("Psitticosaurus") dinosaurs.Add("Caudipteryx") dinosaurs.Add("Compsognathus") dinosaurs.Add("Muttaburrasaurus") 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") Console.WriteLine(vbLf & "dinosaurs(2): {0}", dinosaurs(2)) Console.WriteLine(vbLf & "dinosaurs(2) = ""Microraptor""") dinosaurs(2) = "Microraptor" Console.WriteLine(vbLf & "Remove(""Microraptor"")") dinosaurs.Remove("Microraptor") Console.WriteLine(vbLf & "RemoveAt(0)") dinosaurs.RemoveAt(0) Display(dinosaurs) 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 Private Shared Sub ChangedHandler(ByVal source As Object, _ ByVal e As DinosaursChangedEventArgs) If e.ChangeType = ChangeType.Replaced Then Console.WriteLine("{0} was replaced with {1}", _ e.ChangedItem, e.ReplacedWith) ElseIf e.ChangeType = ChangeType.Cleared Then Console.WriteLine("The dinosaur list was cleared.") Else Console.WriteLine("{0} was {1}.", _ e.ChangedItem, e.ChangeType) End If End Sub End Class ' This code example produces the following output: ' 'Psitticosaurus was Added. 'Caudipteryx was Added. 'Compsognathus was Added. 'Muttaburrasaurus was Added. ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'IndexOf("Muttaburrasaurus"): 3 ' 'Contains("Caudipteryx"): True ' 'Insert(2, "Nanotyrannus") 'Nanotyrannus was Added. ' 'dinosaurs(2): Nanotyrannus ' 'dinosaurs(2) = "Microraptor" 'Nanotyrannus was replaced with Microraptor ' 'Remove("Microraptor") 'Microraptor was Removed. ' 'RemoveAt(0) 'Psitticosaurus was Removed. ' 'Caudipteryx 'Compsognathus 'Muttaburrasaurus
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.