private void CmbHospital_SelectedIndexChanged(object sender, EventArgs e) { cmbPolyclinic.Items.Clear(); cmbPolyclinic.Text = string.Empty; polyclinicController = new PolyclinicController(); polyclinics = polyclinicController.GetAll(); int hospitalId = ((Hospital)(cmbHospital.SelectedItem)).HospitalId; foreach (Polyclinic polyclinic in polyclinics) { if (polyclinic.HospitalId == hospitalId) { cmbPolyclinic.Items.Add(polyclinic.PolyclinicName); } } hospitalDepartmentController = new HospitalDepartmentController(); hospitalDepartments = hospitalDepartmentController.GetAll(); foreach (HospitalDepartment department in hospitalDepartments) { appointmentController = new AppointmentController(); cmbDepartment.DataSource = appointmentController.ListDepartment(hospitalId); cmbDepartment.DisplayMember = "DepartmentName"; cmbDepartment.ValueMember = "DepartmentId"; } cmbDoctor.SelectedIndex = -1; cmbDoctor.Text = string.Empty; cmbHour.DataSource = null; }