Array.Reverse Method (Array)

 
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Reverses the sequence of the elements in the entire one-dimensional Array.

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

Public Shared Sub Reverse (
	array As Array
)

Parameters

array
Type: System.Array

The one-dimensional Array to reverse.

Exception Condition
ArgumentNullException

array is null.

RankException

array is multidimensional.

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 the Length of array.

As the following example shows, the Reverse method can be used to reverse a jagged array. It initializes a jagged array with one element for each month of the current year in the current culture's calendar. Each element contains an array with as many elements as that month has days. The example displays the contents of the array, calls the Reverse method, and then displays the contents of the reversed array.

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim nMonths As Integer = DateTimeFormatInfo.CurrentInfo.Calendar.GetMonthsInYear(Date.Now.Year)
      Dim months()() As Integer = New Integer(nMonths - 1)() {}

      ' Populate elements with number of days in month.
      For ctr As Integer = 0 To months.GetUpperBound(0)
         Dim daysInMonth As Integer = DateTime.DaysInMonth(Date.Now.Year, ctr + 1)
         months(ctr) = New Integer(daysInMonth - 1) {}
         For ctr2 As Integer = 1 To daysInMonth
            months(ctr)(ctr2 - 1) = ctr2
         Next
      Next

      For Each _month In months
         For each _day In _month
            Console.Write("{0} ", _day)
         Next   
         Console.WriteLine()
      Next
      Console.WriteLine()

      Console.WriteLine("About to reverse array.")
      Console.WriteLine()
      Array.Reverse(months)

      For Each _month In months
         For each _day In _month
            Console.Write("{0} ", _day)
         Next   
         Console.WriteLine()
      Next
   End Sub
End Module
' The example displays output similar to the following:
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    
'    About to reverse array.
'    
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
'    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

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

Imports System
Imports Microsoft.VisualBasic

Public Class SamplesArray    

    Public Shared Sub Main()

        ' 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.
        Console.WriteLine("The Array initially contains the " _
           + "following values:")
        PrintIndexAndValues(myArray)

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

        ' Displays the values of the Array.
        Console.WriteLine("After reversing:")
        PrintIndexAndValues(myArray)
    End Sub 'Main



    Public Shared Sub PrintIndexAndValues(myArray As Array)
        Dim i As Integer
        For i = myArray.GetLowerBound(0) To myArray.GetUpperBound(0)
            Console.WriteLine(ControlChars.Tab + "[{0}]:" + ControlChars.Tab _
               + "{1}", i, myArray.GetValue(i))
        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]:    dog
'     [1]:    lazy
'     [2]:    the
'     [3]:    over
'     [4]:    jumps
'     [5]:    fox
'     [6]:    brown
'     [7]:    quick
'     [8]:    The 

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