Dim stb As New System.Text.StringBuilder("assdasdsdf1234567890" & vbCrLf & _
  "qwqweqeqwe")
 
Using fs As New IO.FileStream _
     ("c:\daten\from_stb.txt", IO.FileMode.Create, IO.FileAccess.Write, _
     IO.FileShare.None)
 
     For i As Integer = 0 To stb.Length - 1
         fs.WriteByte(CByte(AscW(stb(i))))          
     Next i
End Using