Binaryworld - FlipCase - Inverting the case of all characters of the input string ... [ VB.net -> String ]

' Invert the case of all characters of the input string
'
' Examples:
'  Debug.WriteLine(FlipCase("Hello World")) ' => hELLO wORLD
'  Debug.WriteLine(FlipCase("hELLO wORLD")) ' => Hello World
'  Debug.WriteLine(FlipCase("3) this is message n. 3")) ' => 3) THIS IS
' MESSAGE N. 3

Function FlipCase(ByVal input As String) As String
  Dim i As Integer
  Dim res As New System.Text.StringBuilder(input.Length)

  For i = 0 To input.Length - 1
    ' if the char is lowercase, add to the stringbuilder the char in
    ' uppercase
    If Char.IsLower(input.Chars(i)) Then
      res.Append(Char.ToUpper(input.Chars(i)))
    ElseIf Char.IsUpper(input.Chars(i)) Then
      ' if the char is uppercase, add to the stringbuilder the char in
      ' lowercase
      res.Append(Char.ToLower(input.Chars(i)))
    Else
      ' if the char is a digit or another non-letter char, add it as it is
      res.Append(input.Chars(i))
    End If
  Next
  Return res.ToString()
End Function