private void buttonAddDoctor_Click(object sender, EventArgs e)
        {
            this.Hide();
            DoctorInfo s = new DoctorInfo();

            s.Show();
        }
        private void buttonBack_Click(object sender, EventArgs e)
        {
            this.Hide();
            DoctorInfo m = new DoctorInfo();

            m.Closed += (s, args) => this.Close();
            m.Show();
        }