List(Of T).Insert Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Inserts an element into the List(Of T) at the specified index.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
- Type: System.Int32
The zero-based index at which item should be inserted.
- item
- Type: T
The object to insert. The value can be Nothing for reference types.
Implements
IList(Of T).Insert(Int32, T)| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | index is less than 0. -or- index is greater than Count. |
List(Of T) accepts Nothing as a valid value for reference types and allows duplicate elements.
If Count already equals Capacity, the capacity of the List(Of T) is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added.
If index is equal to Count, item is added to the end of List(Of T).
This method is an O(n) operation, where n is Count.
The following code example demonstrates the Insert method, along with various other properties and methods of the List(Of T) generic class. After the list is created, elements are added. The Insert method is used to insert an item into the middle of the list. The item inserted is a duplicate, which is later removed using the Remove method.
Imports System.Collections.Generic Public Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Dim dinosaurs As New List(Of String) outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf dinosaurs.Add("Tyrannosaurus") dinosaurs.Add("Amargasaurus") dinosaurs.Add("Mamenchisaurus") dinosaurs.Add("Deinonychus") dinosaurs.Add("Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text &= String.Format(vbLf & "Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf outputBlock.Text &= vbLf & String.Format("Contains(""Deinonychus"": {0}", _ dinosaurs.Contains("Deinonychus")) & vbCrLf outputBlock.Text &= String.Format(vbLf & "Insert(2, ""Compsognathus"")") & vbCrLf dinosaurs.Insert(2, "Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next outputBlock.Text &= String.Format(vbLf & "dinosaurs(3): {0}", dinosaurs(3)) & vbCrLf outputBlock.Text &= vbLf & "Remove(""Compsognathus"")" & vbCrLf dinosaurs.Remove("Compsognathus") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next dinosaurs.TrimExcess() outputBlock.Text &= vbLf & "TrimExcess()" & vbCrLf outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf dinosaurs.Clear() outputBlock.Text &= vbLf & "Clear()" & vbCrLf outputBlock.Text &= String.Format("Capacity: {0}", dinosaurs.Capacity) & vbCrLf outputBlock.Text &= String.Format("Count: {0}", dinosaurs.Count) & vbCrLf End Sub End Class ' This code example produces the following output: ' 'Capacity: 0 ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'Capacity: 8 'Count: 5 ' 'Contains("Deinonychus"): True ' 'Insert(2, "Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Compsognathus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'dinosaurs(3): Mamenchisaurus ' 'Remove("Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'TrimExcess() 'Capacity: 5 'Count: 5 ' 'Clear() 'Capacity: 5 'Count: 0