Bus B1 can directly take you from Xiasha to the Brand New Eastern bus station. There you can take bus to Jiashan. Well, there is direct bus from the General Bus Station Jiubao Xiasha to Xitang. You can also go there to tale it.
There is direct bus from Xitang to Shanghai. It runs from 06:20 to 18:00.

...Thanks Mr david. However I do know (because I have taken it so many time) that the B1 does not take you to the NEW Eastern Bus Station.
It did when it was the OLD Eastern Bus Station. This new one opened in October last year and the old one on the B1's route has long closed down. So I want to know how to get to the new Eastern Bus Station. Thank you.

You can take Bus at Hangzhou Transport Center Station, there are buses go directly to Xitang at 09:25, 11:20, 13:50.

To Jiashan, buses can only be taken at Tranport Central Station, there are more than 20 buses a day.
From Hangzhou to Shanghai , you can take bus at Hangzhou South Bus Station or Tranport Center Station.

The following city buses can get to Hangzhou Transport Center Station: 69, 100, 101, 104, 111, 314, 328, 508, 684, 848