private void btnSave_Click(object sender, EventArgs e)
        {
            telephone = new Telephone();

            telephone.Manufacturer = txtManufacturer.Text;
            telephone.Model = txtModel.Text;
            telephone.PhoneNumber = txtPhoneNum.Text;
            numberToDial = txtNumberToDial.Text;

            // have the user pick a file if they have not done so already
            if (fileName == "")
            {
                if (saveFileDialogTelephoneEntryForm.ShowDialog() == DialogResult.OK)
                {
                    fileName = saveFileDialogTelephoneEntryForm.FileName;
                }
            }

            // open the file
            fs = new FileStream(fileName, FileMode.Append, FileAccess.Write);
            w = new BinaryWriter(fs);
            // write the data to the file
            telephone.saveDataTo(w);
            // close the file in case we need to open for reading
            w.Close();
            fs.Close();

            // display the data
            txtOutput.Text = telephone.ToString() + Environment.NewLine +
                                "Phone # to dial: " + numberToDial;

            // clear the fields
            txtManufacturer.Clear();
            txtModel.Clear();
            txtPhoneNum.Clear();
            txtNumberToDial.Clear();
        }
        private void btnShowPhones_Click(object sender, EventArgs e)
        {
            int i = 0;

            TelephoneListForm showPhonesForm = new TelephoneListForm();

            if (openFileDialogTelephoneEntryForm.ShowDialog() == DialogResult.OK)
            {
                fs = (FileStream)openFileDialogTelephoneEntryForm.OpenFile();
                r = new BinaryReader(fs);

                while (r.BaseStream.Position < r.BaseStream.Length)
                {
                    telephone = new Telephone();
                    telephone.readDataFrom(r);
                    showPhonesForm.txtPhonesEntered.AppendText("=== Telephone " + (i + 1).ToString() + " ===" + Environment.NewLine);
                    showPhonesForm.txtPhonesEntered.AppendText(telephone.ToString() + Environment.NewLine);
                    showPhonesForm.txtPhonesEntered.AppendText(Environment.NewLine);
                    i++;
                }

                showPhonesForm.toolStripStatusLabelTelephoneListForm.Text = "A total of " + i.ToString() + " telephones.";
            }

            // show the form
            showPhonesForm.Show();
        }