Dim ch As Char
                Dim strCode As String
                Dim Code, i, Number, numberInFile As Short
                Dim Decrypt As String = ""
 
                ...
 
                numberInFile = txtEingabe.Text.Length
 
                For i = 0 To numberInFile - 1
                    Number = txtEingabe.Text.Substring(i, 1)
                    ch = Chr(Number Xor Code) 'Mit Xor umwandeln
                    Decrypt = Decrypt & ch 'Zeichenfolge erstellen
                Next