Reverse String

A String contains individual characters. The order of these characters can be reversed. But we cannot change a string directly.

Implementation notes

In VB.NET we reverse a string using the ToCharArray function. We then use the Array.Reverse Sub, and finally the String constructor.

An example

In Reverse() we store the value returned by ToCharArray in a local variable. Next pass that variable to the Array.Reverse subroutine.

Module Module1
    Sub Main()
        ' Test.
        Console.WriteLine(Reverse("bird"))
        Console.WriteLine(Reverse("cat"))
    End Sub

    ''' <summary>
    ''' Reverse input string.
    ''' </summary>
    Function Reverse(ByVal value As String) As String
        ' Convert to char array.
        Dim arr() As Char = value.ToCharArray()
        ' Use Array.Reverse function.
        Array.Reverse(arr)
        ' Construct new string.
        Return New String(arr)
    End Function
End Module
drib
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Interviews

Readers have commented that in interview questions, the classic question of writing a method to reverse a string often have some constraints.

Module Program
    Sub Main()
        Array.Reverse("test")
    End Sub
End Module
Error BC30311
Value of type 'String' cannot be converted to 'Array'.

A summary

Strings in VB.NET cannot be manipulated directly. They are immutable. You must convert them to character arrays with the ToCharArray function.