How to preselect drop-down list in page 2 with assigned value from page 1 via response.redirect

Question

Hi,
I'm doing a response direct from page 1 with values from page 1 transmitted in url. How to get these values preselected in user controls (drop-down lists) in page 2?
Values in page 2 user controls are populated when page 2 loads (within if (!Page.IsPostBack) {...}) and I want transmitted values in url from page 1 to be preselected in user controls (drop-down lists) in page 2.
Thx in advance!