Array.Reverse Example
This page was last reviewed on Feb 18, 2022.
Dot Net Perls
Array.Reverse. This inverts the order of elements. It can act upon an entire array, or just part of an array (a range). It can be used to sort in reverse—simply call Reverse after Sort.
An internal method. Array.Reverse uses an internal, optimized method. It would be hard to develop a faster one in VB.NET code. Usually this built-in is preferred.
An example. Let's begin with this program. The initial array is pointed to by the reference variable a. Then, we reverse that array with Array.Reverse(a). The return value is not used.
Finally We reverse only the first two elements by using the parameters 0 (the first index) and 2 (the count of elements to reverse).
Tip Reverse is found on the Array type. It is a static (shared) function. We call it with a composite name.
Module Module1 Sub Main() Dim a() As Integer = {1, 4, 6, 10} For Each v As Integer In a Console.WriteLine(v) Next Console.WriteLine() ' Reverse entire array. Array.Reverse(a) For Each v As Integer In a Console.WriteLine(v) Next Console.WriteLine() ' Reverse part of array. Array.Reverse(a, 0, 2) For Each v As Integer In a Console.WriteLine(v) Next End Sub End Module
1 4 6 10 10 6 4 1 6 10 4 1
A discussion. The implementation of .NET methods is relevant because it tells us whether they will be efficient. Array.Reverse calls an internal method called TrySZReverse.
Tip This is in unmanaged code. It is likely faster in most situations because of unmanaged optimizations.
Reverse string. With Array.Reverse we can reverse the ordering of chars in a string. We first use ToCharArray to convert a string to a char array.
String Reverse
A summary. We reverse an entire array or only parts (ranges) of an array with Array.Reverse. The type of the elements in the array are not important—they are not sorted or changed.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Feb 18, 2022 (edit link).
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