Using fs As New IO.FileStream(datei, IO.FileMode.Open, _
    IO.FileAccess.Read, IO.FileShare.None), _
    br As New IO.BinaryReader(fs, System.Text.UTF8Encoding.UTF8)
    fs.Position = ...
 
    'direkte Zuweisung der Zeichen auf Stringvariable
    Dim text As String = br.ReadChars(100) 
    '......             
End Using

    fs.position = ....
    Dim bytes(99) as byte 
    fs.Read(bytes, 0, 100) 'Bytearray lesen
 
    'Nur bei Bedarf in Bytes in Text wandeln
    Dim Text As String = ByteArrayToTextString(bytes)

Public Function ByteArrayToTextString(ByVal bytes() As Byte) As String
   Dim enc As System.Text.Encoding = System.Text.UTF8Encoding.UTF8
   Return enc.GetString(bytes)
End Function