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)

public static void Reverse(
	Array array,
	int index,
	int length


Type: System.Array

The one-dimensional Array to reverse.

Type: System.Int32

The starting index of the section to reverse.

Type: System.Int32

The number of elements in the section to reverse.

Exception Condition

array is null.


array is multidimensional.


index is less than the lower bound of array.


length is less than zero.


index and length do not specify a valid range in array.

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.

TheReverse method can be used to reverse a jagged array.

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

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

using System;
public class SamplesArray  {

   public static void Main()  {

      // 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.
      Console.WriteLine( "The Array initially contains the following values:" );
      PrintIndexAndValues( myArray );

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

      // Displays the values of the Array.
      Console.WriteLine( "After reversing:" );
      PrintIndexAndValues( myArray );

   public static void PrintIndexAndValues( Array myArray )  {
      for ( int i = myArray.GetLowerBound(0); i <= myArray.GetUpperBound(0); i++ )
         Console.WriteLine( "\t[{0}]:\t{1}", i, myArray.GetValue( i ) );
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

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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