Well, I think it is difficult to hail a taxi to Shanghai after 22:00 and the taxi fare is around 700yuan, very expensive. So, the best solution is to stay in Hangzhou for one night and take train to Shanghai next morning. And, it seems too late to go to the downtown area for a hotel, so you could stay at the 2-star Holiday Star Airport Hotel in Xiaoshan Airport. The next morning, take the airport shuttle bus to Hangzhou Railway Station and catch the bullet train No.D5658 which leaves for Shanghai at 10:07.
Hope this helps!