[VB.NET]: Memorizzare valori esadecimali di un file in un array

[flash.tato]

Imports System.IO 
................
  Dim str As New FileStream(TextBox1.Text, FileMode.Open, FileAccess.ReadWrite)
  Dim ttf As Byte
  Dim byte As String
  ttf = str.Read()
  byte = Hex (ttf)

A me dà errore