private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
 {
     comboBox3.Items.Clear();
     textBox20.Clear();
     textBox14.Clear();
     textBox2.Clear();
     comboBox3.Items.Add("Select Doctor");
     comboBox3.Text = "Select Doctor";
     if (comboBox2.Text != "Doctor Qualification")
     {
         PlaceAppointmentmysql DoctorsNames = new PlaceAppointmentmysql();
         List <string>         names        = DoctorsNames.FindDoctorsNAMEbyqualification(comboBox2.Text);
         foreach (var item in names)
         {
             comboBox3.Items.Add(item.ToString());
             comboBox3.Enabled = true;
         }
     }
     else
     {
         comboBox3.Enabled = false;
     }
 }