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ArrayList.Reverse Method

Definition

Namespace:
System.Collections
Assemblies:
mscorlib.dll, System.Collections.NonGeneric.dll
Assemblies:
netstandard.dll, System.Runtime.dll
Assembly:
System.Collections.NonGeneric.dll
Assembly:
System.Runtime.Extensions.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll

Reverses the order of the elements in the ArrayList or a portion of it.

Overloads

Reverse()

Reverses the order of the elements in the entire ArrayList.
Reverse(Int32, Int32)

Reverses the order of the elements in the specified range.

Reverse()

Source:
ArrayList.cs
Source:
ArrayList.cs
Source:
ArrayList.cs
Source:
ArrayList.cs

Reverses the order of the elements in the entire ArrayList.

public:
 virtual void Reverse();
public virtual void Reverse();
abstract member Reverse : unit -> unit
override this.Reverse : unit -> unit
Public Overridable Sub Reverse ()

Exceptions

NotSupportedException

The ArrayList is read-only.

Examples

The following code example shows how to reverse the sort order of the values in an ArrayList.

using System;
using System.Collections;
public class SamplesArrayList  {

   public static void Main()  {

      // Creates and initializes a new ArrayList.
      ArrayList myAL = new ArrayList();
      myAL.Add( "The" );
      myAL.Add( "quick" );
      myAL.Add( "brown" );
      myAL.Add( "fox" );
      myAL.Add( "jumps" );
      myAL.Add( "over" );
      myAL.Add( "the" );
      myAL.Add( "lazy" );
      myAL.Add( "dog" );

      // Displays the values of the ArrayList.
      Console.WriteLine( "The ArrayList initially contains the following values:" );
      PrintValues( myAL );

      // Reverses the sort order of the values of the ArrayList.
      myAL.Reverse();

      // Displays the values of the ArrayList.
      Console.WriteLine( "After reversing:" );
      PrintValues( myAL );
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.WriteLine( "   {0}", obj );
      Console.WriteLine();
   }
}


/*
This code produces the following output.

The ArrayList initially contains the following values:
   The
   quick
   brown
   fox
   jumps
   over
   the
   lazy
   dog

After reversing:
   dog
   lazy
   the
   over
   jumps
   fox
   brown
   quick
   The
*/

Imports System.Collections

Public Class SamplesArrayList    
    
    Public Shared Sub Main()
        
        ' Creates and initializes a new ArrayList.
        Dim myAL As New ArrayList()
        myAL.Add("The")
        myAL.Add("quick")
        myAL.Add("brown")
        myAL.Add("fox")
        myAL.Add("jumps")
        myAL.Add("over")
        myAL.Add("the")
        myAL.Add("lazy")
        myAL.Add("dog")
        
        ' Displays the values of the ArrayList.
        Console.WriteLine("The ArrayList initially contains the " _
           + "following values:")
        PrintValues(myAL)
        
        ' Reverses the sort order of the values of the ArrayList.
        myAL.Reverse()
        
        ' Displays the values of the ArrayList.
        Console.WriteLine("After reversing:")
        PrintValues(myAL)
    End Sub
    
    Public Shared Sub PrintValues(myList As IEnumerable)
        Dim obj As [Object]
        For Each obj In  myList
            Console.WriteLine("   {0}", obj)
        Next obj
        Console.WriteLine()
    End Sub

End Class


' This code produces the following output.
' 
' The ArrayList initially contains the following values:
'    The
'    quick
'    brown
'    fox
'    jumps
'    over
'    the
'    lazy
'    dog
'
' After reversing:
'    dog
'    lazy
'    the
'    over
'    jumps
'    fox
'    brown
'    quick
'    The

Remarks

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

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

Applies to

Reverse(Int32, Int32)

Source:
ArrayList.cs
Source:
ArrayList.cs
Source:
ArrayList.cs
Source:
ArrayList.cs

Reverses the order of the elements in the specified range.

public:
 virtual void Reverse(int index, int count);
public virtual void Reverse(int index, int count);
abstract member Reverse : int * int -> unit
override this.Reverse : int * int -> unit
Public Overridable Sub Reverse (index As Integer, count As Integer)

Parameters

index
Int32

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

count
Int32

The number of elements in the range to reverse.

Exceptions

ArgumentOutOfRangeException

index is less than zero.

-or-

count is less than zero.

ArgumentException

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

NotSupportedException

The ArrayList is read-only.

Examples

The following code example shows how to reverse the sort order of the values in a range of elements in an ArrayList.

using System;
using System.Collections;
public class SamplesArrayList1  {

   public static void Main()  {

      // Creates and initializes a new ArrayList.
      ArrayList myAL = new ArrayList();
      myAL.Add( "The" );
      myAL.Add( "QUICK" );
      myAL.Add( "BROWN" );
      myAL.Add( "FOX" );
      myAL.Add( "jumps" );
      myAL.Add( "over" );
      myAL.Add( "the" );
      myAL.Add( "lazy" );
      myAL.Add( "dog" );

      // Displays the values of the ArrayList.
      Console.WriteLine( "The ArrayList initially contains the following values:" );
      PrintValues( myAL );

      // Reverses the sort order of the values of the ArrayList.
      myAL.Reverse( 1, 3 );

      // Displays the values of the ArrayList.
      Console.WriteLine( "After reversing:" );
      PrintValues( myAL );
   }

   public static void PrintValues( IEnumerable myList )  {
      foreach ( Object obj in myList )
         Console.WriteLine( "   {0}", obj );
      Console.WriteLine();
   }
}


/*
This code produces the following output.

The ArrayList initially contains the following values:
   The
   QUICK
   BROWN
   FOX
   jumps
   over
   the
   lazy
   dog

After reversing:
   The
   FOX
   BROWN
   QUICK
   jumps
   over
   the
   lazy
   dog

*/

Imports System.Collections

Public Class SamplesArrayList

    Public Shared Sub Main()

        ' Creates and initializes a new ArrayList.
        Dim myAL As New ArrayList()
        myAL.Add("The")
        myAL.Add("QUICK")
        myAL.Add("BROWN")
        myAL.Add("FOX")
        myAL.Add("jumps")
        myAL.Add("over")
        myAL.Add("the")
        myAL.Add("lazy")
        myAL.Add("dog")

        ' Displays the values of the ArrayList.
        Console.WriteLine("The ArrayList initially contains the following values:")
        PrintValues(myAL)

        ' Reverses the sort order of the values of the ArrayList.
        myAL.Reverse(1, 3)

        ' Displays the values of the ArrayList.
        Console.WriteLine("After reversing:")
        PrintValues(myAL)

    End Sub

    Public Shared Sub PrintValues(myList As IEnumerable)
        Dim obj As [Object]
        For Each obj In  myList
            Console.WriteLine("   {0}", obj)
        Next obj
        Console.WriteLine()
    End Sub

End Class


' This code produces the following output.
' 
' The ArrayList initially contains the following values:
'    The
'    QUICK
'    BROWN
'    FOX
'    jumps
'    over
'    the
'    lazy
'    dog
'
' After reversing:
'    The
'    FOX
'    BROWN
'    QUICK
'    jumps
'    over
'    the
'    lazy
'    dog

Remarks

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

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

Applies to