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List(Of T).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 
Dim index As Integer 
Dim count As Integer

instance.Reverse(index, count)

Parameters

index
Type: System.Int32

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

count
Type: System.Int32

The number of elements in the range to reverse.

ExceptionCondition
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(Of T).

This method uses Array.Reverse to reverse the order of the elements, such that the element at List(Of T)[i], where i is any index within the range, moves to List(Of T)[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 T) 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 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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