Not clear previous data in list<T>
I insert data to list<T> and bind it to data-grid.

And when i try to reinsert data , the previous data is cleared . 

I want the previous data not clear and new data add in list

     int count = 0;
        private void button_insert_Click(object sender, RoutedEventArgs e)
        {
            Table_infodetail_print tip = new Table_infodetail_print();
            List<Table_infodetail_print> ltip = new List<Table_infodetail_print>();
            tip.nation_code = nation_code;
            tip.services_discription = comboBox_services.SelectedValue.ToString();
            tip.additional_price = additional_price;
            tip.lot_patient = lot_patient;
            tip.price = price;
            tip.tariff = tariff;
            ltip.Insert(count, tip);
            var select_details = from t in ltip
                                 select t;
            dataGrid_insert_services.ItemsSource = ltip;
            count++;
        }

Please advise me


Not clear previous data in list<T>
===

I insert data to list<T> and bind it to data-grid.

And when i try to reinsert data , the previous data is cleared . 

I want the previous data not clear and new data add in list

     int count = 0;
        private void button_insert_Click(object sender, RoutedEventArgs e)
        {
            Table_infodetail_print tip = new Table_infodetail_print();
            List<Table_infodetail_print> ltip = new List<Table_infodetail_print>();
            tip.nation_code = nation_code;
            tip.services_discription = comboBox_services.SelectedValue.ToString();
            tip.additional_price = additional_price;
            tip.lot_patient = lot_patient;
            tip.price = price;
            tip.tariff = tariff;
            ltip.Insert(count, tip);
            var select_details = from t in ltip
                                 select t;
            dataGrid_insert_services.ItemsSource = ltip;
            count++;
        }

Please advise me

