Private dateiname As String = "F:\test\buecher.dat"
 
    Sub buchdateifuellen(ByVal buchnr As String, ByVal titel As String, ByVal _
      autor As String)
        Dim fs As New IO.FileStream(dateiname, IO.FileMode.OpenOrCreate, _
        IO.FileAccess.Write)
        Dim bw As New IO.BinaryWriter(fs)
        fs.Seek(0, IO.SeekOrigin.End)
        bw.Write(buchnr)
        bw.Write(titel)
        bw.Write(autor)
        bw.Close()
    End Sub
 
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) _
      Handles Button1.Click
        buchdateifuellen(TextBox1.Text, TextBox2.Text, TextBox3.Text)
    End Sub
 
    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) _
      Handles Button2.Click
        Using fs As New IO.FileStream(dateiname, IO.FileMode.Open, _
        IO.FileAccess.Read),
            br As New IO.BinaryReader(fs)
            ListBox1.Items.Clear()
            While fs.Position < fs.Length
                ListBox1.Items.Add(br.ReadString() & " " & br.ReadString() & "" & _
                  "" & br.ReadString())
            End While
        End Using
    End Sub
 
    Private Sub Button3_Click(sender As System.Object, e As System.EventArgs) _
      Handles Button3.Click
        IO.File.Delete(dateiname)
    End Sub

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Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist