Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button4.Click
        Dim fs As New System.IO.FileStream(Datei, IO.FileMode.Open)
        Dim br As New System.IO.BinaryReader(fs)
        Dim bytes() As System.Byte
        Dim länge As Integer
        If CheckBox1.Checked = True Then 'gesamte Datei einlesen
            länge = fs.Length
            bytes = br.ReadBytes(fs.Length) 'gesamte Datei auslesen
        Else
            länge = Convert.ToInt64(TextBox3.Text)
            bytes = br.ReadBytes(länge)
        End If
 
        br.Close()
        fs.Close()
        Label56.Text = länge / Convert.ToInt64(TextBox7.Text)
 
        ProgressBar1.Visible = True
        ProgressBar1.Maximum = länge
        ProgressBar1.Value = 0
 
         For Each b As System.Byte In bytes
            Me.RichTextBox1.Text += System.String.Format("{0:X2}", b)
            'Me.TextBox1.Text += System.String.Format("{0:X2}", b)
            ProgressBar1.Value = ProgressBar1.Value + 1
        Next
 
        MsgBox("Einlesevorgang erfolgreich beendet", MsgBoxStyle.Information)
        ProgressBar1.Value = 0
        ProgressBar1.Visible = False
    End Sub