private void bttn_newPatient_Click(object sender, EventArgs e)
        {
            using (var formPatient = new View.FrmPatient())
            {
                var result = formPatient.ShowDialog();

                if (result == DialogResult.OK)
                {
                    var patient = formPatient.patient;

                    InitializePatients();

                    selectedPatient          = patient;
                    lbPatients.SelectedIndex = activePatients.Select(o => o.Id).ToList().IndexOf(selectedPatient.Id);
                }
            }
        }
        private void bttn_editPatient_Click(object sender, EventArgs e)
        {
            if (selectedPatient != null)
            {
                using (var formPatient = new View.FrmPatient(selectedPatient))
                {
                    var result = formPatient.ShowDialog();

                    if (result == DialogResult.OK)
                    {
                        var patient = formPatient.patient;

                        InitializePatients();

                        selectedPatient          = patient;
                        lbPatients.SelectedIndex = activePatients.Select(o => o.Id).ToList().IndexOf(selectedPatient.Id);
                    }
                }
            }
            else
            {
                MessageBox.Show("Um die Patientendaten eines bestehenden Patienten zu bearbeiten, müssen sie zunächst einen Patienten auswählen.");
            }
        }