private void button2_Click(object sender, EventArgs e) { Clera(); panel2.Visible = true; dateTimePicker1.MinDate = DateTime.Today; PlaceAppointmentmysql doctorsqualifications = new PlaceAppointmentmysql(); List <string> qualifications = doctorsqualifications.FindDoctorsQualifications(); List <string> patientsID = doctorsqualifications.FindAllPatintsID(); List <string> floors = doctorsqualifications.FindFloors();//??? foreach (var item in qualifications) { comboBox2.Items.Add(item); } foreach (var item in patientsID) { comboBox1.Items.Add(item); } foreach (var item in floors) { comboBox4.Items.Add(item); } }