Question

How to invert the letters case in a String uppercase to lowercase and lowercase to uppercase in VB.NET

Answer 1

Imports System.Text

Module Module1

    Sub Main()

        Dim s As String = "VB.net Programming"

        s = InvertLettersCase(s)
        Console.WriteLine(s)

        Console.WriteLine(InvertLettersCase("Programming"))

    End Sub


    Public Function InvertLettersCase(s As String) As String

        Dim sb As New StringBuilder()

        For Each ch As Char In s
            If Char.IsLower(ch) Then
                sb.Append(Char.ToUpper(ch))
            ElseIf Char.IsUpper(ch) Then
                sb.Append(Char.ToLower(ch))
            Else
                sb.Append(ch)
            End If
        Next

        Return sb.ToString()

    End Function

End Module

' run:
' 
' vb.NET pROGRAMMING
' pROGRAMMING

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Answer 2

Imports System.Text

Module Module1

    Sub Main()

        Dim s As String = "VB.net Programming"

        s = InvertLettersCase(s)
        Console.WriteLine(s)

        Console.WriteLine(InvertLettersCase("Programming"))

    End Sub

    Public Function InvertCharCase(ch As Char) As Char
        If Char.IsLower(ch) Then Return Char.ToUpper(ch)
        If Char.IsUpper(ch) Then Return Char.ToLower(ch)
        Return ch
    End Function


    Public Function InvertLettersCase(s As String) As String

        Dim sb As New StringBuilder()

        For Each ch As Char In s
            sb.Append(InvertCharCase(ch))
        Next

        Return sb.ToString()

    End Function

End Module

' run:
' 
' vb.NET pROGRAMMING
' pROGRAMMING

 

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Answer 3

Module Module1

    Sub Main()

        Dim s As String = "VB.net Programming"

        s = InvertLettersCase(s)
        Console.WriteLine(s)

        Console.WriteLine(InvertLettersCase("Programming"))

    End Sub

    Public Function InvertLettersCase(s As String) As String

        Dim rv

        rv = New String(s.Select(Function(c)
                                     Return If(Char.IsLower(c), Char.ToUpper(c), Char.ToLower(c))
                                 End Function).ToArray())
        Return rv

    End Function

End Module

' run:
' 
' vb.NET pROGRAMMING
' pROGRAMMING

 

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