bytes = Byte.Parse(RichTextBox1.Text, Globalization.NumberStyles.HexNumber)

' Anzahl der Bytes berechnen
Dim len As Integer = RichTextBox1.Text.Length \ 2
 
' Byte-Array in das die Daten kommen
Dim bytes(len - 1) As Byte
 
' Text schrittweise in Bytes umwandeln.
For i As Integer = 0 To len - 1
    bytes(i) = Byte.Parse( _
        RichTextBox1.Text.Substring(i * 2, 2), _
        Globalization.NumberStyles.HexNumber)
Next

bytes = System.Text.Encoding.UTF8.GetBytes(RichTextBox1.Text)

sb.Append(String.Format("{0:X2}", Hex(b)))

sb.Append(String.Format(Byte.Parse(b,  Globalization.NumberStyles.HexNumber)))

Sub SaveRTB1(AusgabeDatei As String)
    ' Anzahl der Bytes berechnen
    Dim len As Integer = RichTextBox1.Text.Length \ 2
 
    Using fs As New FileStream(AusgabeDatei, FileMode.Create, FileAccess.Write)
        Using writer As New BinaryWriter(fs)
            ' Text schrittweise in Bytes umwandeln und speichern.
            For i As Integer = 0 To len - 1
                Dim b As Byte = Byte.Parse( _
                    RichTextBox1.Text.Substring(i * 2, 2), _
                    Globalization.NumberStyles.HexNumber)
                writer.Write(b)
            Next
            writer.Close()
        End Using
    End Using
End Sub