public void Serialize()
 {
     try
     {
         if (File.Exists("db.xml"))
         {
             File.Delete("db.xml");
         }
         using (Stream textWriter = File.Open("db.xml", FileMode.OpenOrCreate))
         {
             XmlSerializer serializer = new XmlSerializer(classifier.GetType());
             serializer.Serialize(textWriter, classifier);
         }
     }
     catch (Exception e)
     {
         MessageBox.Show(e.Message);
     }
 }