List(Of T).RemoveAt Method (Int32)
.NET Framework (current version)
Removes the element at the specified index of the List(Of T).
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
-
Type:
System.Int32
The zero-based index of the element to remove.
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException |
When you call RemoveAt to remove an item, the remaining items in the list are renumbered to replace the removed item. For example, if you remove the item at index 3, the item at index 4 is moved to the 3 position. In addition, the number of items in the list (as represented by the Count property) is reduced by 1.
This method is an O(n) operation, where n is (Count - index).
The following example demonstrates how to add, remove, and insert a simple business object in a List(Of T).
Imports System.Collections.Generic ' Simple business object. A PartId is used to identify the type of part ' but the part name can change. Public Class Part Implements IEquatable(Of Part) Public Property PartName() As String Get Return m_PartName End Get Set(value As String) m_PartName = Value End Set End Property Private m_PartName As String Public Property PartId() As Integer Get Return m_PartId End Get Set(value As Integer) m_PartId = Value End Set End Property Private m_PartId As Integer Public Overrides Function ToString() As String Return "ID: " & PartId & " Name: " & PartName End Function Public Overrides Function Equals(obj As Object) As Boolean If obj Is Nothing Then Return False End If Dim objAsPart As Part = TryCast(obj, Part) If objAsPart Is Nothing Then Return False Else Return Equals(objAsPart) End If End Function Public Overrides Function GetHashCode() As Integer Return PartId End Function Public Overloads Function Equals(other As Part) As Boolean _ Implements IEquatable(Of Part).Equals If other Is Nothing Then Return False End If Return (Me.PartId.Equals(other.PartId)) End Function ' Should also override == and != operators. End Class Public Class Example Public Shared Sub Main() ' Create a list of parts. Dim parts As New List(Of Part)() ' Add parts to the list. parts.Add(New Part() With { _ .PartName = "crank arm", _ .PartId = 1234 _ }) parts.Add(New Part() With { _ .PartName = "chain ring", _ .PartId = 1334 _ }) parts.Add(New Part() With { _ .PartName = "regular seat", _ .PartId = 1434 _ }) parts.Add(New Part() With { _ .PartName = "banana seat", _ .PartId = 1444 _ }) parts.Add(New Part() With { _ .PartName = "cassette", _ .PartId = 1534 _ }) parts.Add(New Part() With { _ .PartName = "shift lever", _ .PartId = 1634 _ }) ' Write out the parts in the list. This will call the overridden ToString method ' in the Part class. Console.WriteLine() For Each aPart As Part In parts Console.WriteLine(aPart) Next ' Check the list for part #1734. This calls the IEquitable.Equals method ' of the Part class, which checks the PartId for equality. Console.WriteLine(vbLf & "Contains(""1734""): {0}", parts.Contains(New Part() With { _ .PartId = 1734, _ .PartName = "" _ })) ' Insert a new item at position 2. Console.WriteLine(vbLf & "Insert(2, ""1834"")") parts.Insert(2, New Part() With { _ .PartName = "brake lever", _ .PartId = 1834 _ }) 'Console.WriteLine(); For Each aPart As Part In parts Console.WriteLine(aPart) Next Console.WriteLine(vbLf & "Parts[3]: {0}", parts(3)) Console.WriteLine(vbLf & "Remove(""1534"")") ' This will remove part 1534 even though the PartName is different, ' because the Equals method only checks PartId for equality. parts.Remove(New Part() With { _ .PartId = 1534, _ .PartName = "cogs" _ }) Console.WriteLine() For Each aPart As Part In parts Console.WriteLine(aPart) Next Console.WriteLine(vbLf & "RemoveAt(3)") ' This will remove part at index 3. parts.RemoveAt(3) Console.WriteLine() For Each aPart As Part In parts Console.WriteLine(aPart) Next End Sub ' ' This example code produces the following output: ' ID: 1234 Name: crank arm ' ID: 1334 Name: chain ring ' ID: 1434 Name: regular seat ' ID: 1444 Name: banana seat ' ID: 1534 Name: cassette ' ID: 1634 Name: shift lever ' ' Contains("1734"): False ' ' Insert(2, "1834") ' ID: 1234 Name: crank arm ' ID: 1334 Name: chain ring ' ID: 1834 Name: brake lever ' ID: 1434 Name: regular seat ' ID: 1444 Name: banana seat ' ID: 1534 Name: cassette ' ID: 1634 Name: shift lever ' ' Parts[3]: ID: 1434 Name: regular seat ' ' Remove("1534") ' ' ID: 1234 Name: crank arm ' ID: 1334 Name: chain ring ' ID: 1834 Name: brake lever ' ID: 1434 Name: regular seat ' ID: 1444 Name: banana seat ' ID: 1634 Name: shift lever ' ' ' RemoveAt(3) ' ' ID: 1234 Name: crank arm ' ID: 1334 Name: chain ring ' ID: 1834 Name: brake lever ' ID: 1444 Name: banana seat ' ID: 1634 Name: shift lever ' End Class
Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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