public static void GetHulpBehoevende()
        {
            Connect();

            ReadData("SELECT * FROM ACCOUNT WHERE DISCRIMINATOR = 'H'");

            try
            {
                while (dr.Read())
                {
                    int id;
                    string firstName;
                    string lastName;

                    id = Convert.ToInt32(dr.GetValue(0));
                    firstName = dr.GetString(8);
                    lastName = dr.GetString(9);

                    AccountHandler accounthandler = new AccountHandler();

                    HelpBehoevende helpbehoevende = new HelpBehoevende(id, firstName, lastName);

                    accounthandler.AddHelpbehoevende(helpbehoevende);
                }
            }

            catch (InvalidCastException ex)
            {
                MessageBox.Show(ex.ToString());
            }
            finally
            {
                Disconnect();
            }
        }
        public static void GetVrijwilliger()
        {
            Connect();

            ReadData("SELECT * FROM ACCOUNT WHERE DISCRIMINATOR = 'V'");

            try
            {
                while (dr.Read())
                {
                    int id;
                    string firstName;
                    string lastName;

                    id = dr.GetInt32(0);
                    firstName = dr.GetString(8);
                    lastName = dr.GetString(9);

                    AccountHandler accounthandler = new AccountHandler();

                    Vrijwilliger vrijwilliger = new Vrijwilliger(id, firstName, lastName);

                    accounthandler.AddVrijwilliger(vrijwilliger);
                }
            }

            catch (InvalidCastException ex)
            {
                MessageBox.Show(ex.ToString());
            }
            finally
            {
                Disconnect();
            }
        }