Article
11/18/2011

Array.Reverse Method (Array, Int32, Int32)

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Reverses the sequence of the elements in a range of elements in the one-dimensional Array.

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

Syntax

'Declaration
<SecuritySafeCriticalAttribute> _
Public Shared Sub Reverse ( _
    array As Array, _
    index As Integer, _
    length As Integer _
)

[SecuritySafeCriticalAttribute]
public static void Reverse(
    Array array,
    int index,
    int length
)

Parameters

array
Type: System.Array
The one-dimensional Array to reverse.

index
Type: System.Int32
The starting index of the section to reverse.

length
Type: System.Int32
The number of elements in the section to reverse.

Exceptions

Exception	Condition
ArgumentNullException	array is nulla null reference (Nothing in Visual Basic).
RankException	array is multidimensional.
ArgumentOutOfRangeException	index is less than the lower bound of array. -or- length is less than zero.
ArgumentException	index and length do not specify a valid range in array.

Remarks

After a call to this method, the element at myArray[i], where i is any index in the array, moves to myArray[j], where j equals (myArray.Length + myArray.GetLowerBound(0)) - (i - myArray.GetLowerBound(0)) - 1.

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

Examples

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

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.


Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' Creates and initializes a new Array.
      Dim myArray As Array = Array.CreateInstance(GetType(String), 9)
      myArray.SetValue("The", 0)
      myArray.SetValue("QUICK", 1)
      myArray.SetValue("BROWN", 2)
      myArray.SetValue("FOX", 3)
      myArray.SetValue("jumps", 4)
      myArray.SetValue("over", 5)
      myArray.SetValue("the", 6)
      myArray.SetValue("lazy", 7)
      myArray.SetValue("dog", 8)

      ' Displays the values of the Array.
      outputBlock.Text &= "The Array initially contains the " _
         + "following values:" & vbCrLf
      PrintIndexAndValues(outputBlock, myArray)

      ' Reverses the sort of the values of the Array.
      Array.Reverse(myArray, 1, 3)

      ' Displays the values of the Array.
      outputBlock.Text &= "After reversing:" & vbCrLf
      PrintIndexAndValues(outputBlock, myArray)
   End Sub


   Public Shared Sub PrintIndexAndValues(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal myArray As Array)
      Dim i As Integer
      For i = myArray.GetLowerBound(0) To myArray.GetUpperBound(0)
         outputBlock.Text &= String.Format(ControlChars.Tab + "[{0}]:" + ControlChars.Tab _
            + "{1}", i, myArray.GetValue(i)) & vbCrLf
      Next i
   End Sub
End Class

' This code produces the following output.
' 
' The Array initially contains the following values:
'     [0]:    The
'     [1]:    QUICK
'     [2]:    BROWN
'     [3]:    FOX
'     [4]:    jumps
'     [5]:    over
'     [6]:    the
'     [7]:    lazy
'     [8]:    dog
' After reversing:
'     [0]:    The
'     [1]:    FOX
'     [2]:    BROWN
'     [3]:    QUICK
'     [4]:    jumps
'     [5]:    over
'     [6]:    the
'     [7]:    lazy
'     [8]:    dog

using System;
public class Example
{

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      // Creates and initializes a new Array.
      Array myArray = Array.CreateInstance(typeof(String), 9);
      myArray.SetValue("The", 0);
      myArray.SetValue("QUICK", 1);
      myArray.SetValue("BROWN", 2);
      myArray.SetValue("FOX", 3);
      myArray.SetValue("jumps", 4);
      myArray.SetValue("over", 5);
      myArray.SetValue("the", 6);
      myArray.SetValue("lazy", 7);
      myArray.SetValue("dog", 8);

      // Displays the values of the Array.
      outputBlock.Text += "The Array initially contains the following values:" + "\n";
      PrintIndexAndValues(outputBlock, myArray);

      // Reverses the sort of the values of the Array.
      Array.Reverse(myArray, 1, 3);

      // Displays the values of the Array.
      outputBlock.Text += "After reversing:" + "\n";
      PrintIndexAndValues(outputBlock, myArray);
   }


   public static void PrintIndexAndValues(System.Windows.Controls.TextBlock outputBlock, Array myArray)
   {
      for (int i = myArray.GetLowerBound(0); i <= myArray.GetUpperBound(0); i++)
         outputBlock.Text += String.Format("\t[{0}]:\t{1}", i, myArray.GetValue(i)) + "\n";
   }
}
/* 
This code produces the following output.

The Array initially contains the following values:
    [0]:    The
    [1]:    QUICK
    [2]:    BROWN
    [3]:    FOX
    [4]:    jumps
    [5]:    over
    [6]:    the
    [7]:    lazy
    [8]:    dog
After reversing:
    [0]:    The
    [1]:    FOX
    [2]:    BROWN
    [3]:    QUICK
    [4]:    jumps
    [5]:    over
    [6]:    the
    [7]:    lazy
    [8]:    dog
*/

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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