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List.Reverse Method (Int32, Int32)

Reverses the order of the elements in the specified range.

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

'Declaration
Public Sub Reverse ( _
	index As Integer, _
	count As Integer _
)
'Usage
Dim instance As List(Of T)
Dim index As Integer
Dim count As Integer

instance.Reverse(index, count)
public void Reverse (
	int index, 
	int count
)
public function Reverse (
	index : int, 
	count : int
)
Not applicable.

Parameters

index

The zero-based starting index of the range to reverse.

count

The number of elements in the range to reverse.

Exception typeCondition

ArgumentOutOfRangeException

index is less than 0.

-or-

count is less than 0.

ArgumentException

index and count do not denote a valid range of elements in the List.

This method uses Array.Reverse to reverse the order of the elements, such that the element at List[i], where i is any index within the range, moves to List[j], where j equals index plus index plus count minus i minus 1.

This method is an O(n) operation, where n is Count.

The following code example demonstrates both overloads of the Reverse method. The code example creates a List of strings and adds six strings. The Reverse method overload is used to reverse the list, and then the Reverse(Int32,Int32) method overload is used to reverse the middle of the list, beginning with element 1 and encompassing four elements.

Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)

        dinosaurs.Add("Pachycephalosaurus")
        dinosaurs.Add("Parasauralophus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Coelophysis")
        dinosaurs.Add("Oviraptor")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.Reverse()

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.Reverse(1, 4)

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

    End Sub
End Class

' This code example produces the following output:
'
'Pachycephalosaurus
'Parasauralophus
'Mamenchisaurus
'Amargasaurus
'Coelophysis
'Oviraptor
'
'Oviraptor
'Coelophysis
'Amargasaurus
'Mamenchisaurus
'Parasauralophus
'Pachycephalosaurus
'
'Oviraptor
'Parasauralophus
'Mamenchisaurus
'Amargasaurus
'Coelophysis
'Pachycephalosaurus

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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