private void buttonUpdate_Click(object sender, EventArgs e)
        {
            //updates patient data
            string str = "";

            if (textBoxFirstName.Text == "")
            {
                str = str + "First Name ";
            }
            if (textBoxLastName.Text == "")
            {
                str = str + Environment.NewLine + "Last Name ";
            }

            if (textBoxAge.Text == "")
            {
                str = str + Environment.NewLine + "Age ";
            }
            if (comboBoxSex.SelectedIndex < 0)
            {
                str = str + Environment.NewLine + "Sex ";
            }
            if (comboBoxNationality.SelectedIndex < 0)
            {
                str = str + Environment.NewLine + "Nationality";
            }
            if (str.Length > 0)
            {
                MessageBox.Show(str + Environment.NewLine + "(REQUIRED)");
            }
            else
            {
                Patient     patient     = new Patient();
                Appointment appointment = new Appointment();
                try
                {
                    //patient
                    patient.patientId    = Id;
                    patient.firstName    = this.textBoxFirstName.Text;
                    patient.lastName     = this.textBoxLastName.Text;
                    patient.age          = Convert.ToInt32(this.textBoxAge.Text);
                    patient.sex          = this.comboBoxSex.Text;
                    patient.heightFt     = Convert.ToInt32(this.textBoxHeightFt.Text);
                    patient.heightInch   = Convert.ToInt32(this.textBoxHeightInch.Text);
                    patient.weight       = Convert.ToDecimal(this.textBoxWeight.Text);
                    patient.phone        = Convert.ToInt64(this.textBoxPhone.Text);
                    patient.email        = this.textBoxEmail.Text;
                    patient.address      = this.textBoxAddress.Text;
                    patient.natioinality = Int32.Parse(this.comboBoxNationality.SelectedValue.ToString());
                    //appointment
                    appointment.patientId = Id;
                    appointment.firstName = this.textBoxFirstName.Text;
                    appointment.lastName  = this.textBoxLastName.Text;
                    appointment.phone     = Convert.ToInt64(this.textBoxPhone.Text);
                    PatientManager.patientUpdate(patient);
                    AppointmentManager.AppointmentInfoUpdate(appointment);
                    MessageBox.Show("Success");
                    displayPatient();
                    displayAppointment();
                    clearData();
                }
                catch (System.Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }