Public Class Form1
 
 
Dim file_name As String = ""
 
Private Sub btn_browse_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles btn_browse.Click
        dlg_file_open.ShowDialog()
End Sub
 
Private Sub dlg_file_open_FileOk(ByVal sender As System.Object, ByVal e As _
  System.ComponentModel.CancelEventArgs) Handles dlg_file_open.FileOk
        rtb_text.Clear()
        file_name = dlg_file_open.FileName
        Dim fi As FileInfo = New FileInfo(file_name)
        Dim fs As FileStream = _
        New FileStream(file_name, FileMode.Open)
        Dim byteArr(fi.Length - 1) As Byte
        ' Datenstrom in ein Byte-Array einlesen  
        fs.Read(byteArr, 0, fi.Length)
        'Ausgabe in RichTextBox
        Dim i As Integer
        For i = 0 To fi.Length - 1
            rtb_text.AppendText(Chr(byteArr(i)))
        Next i
End Sub