How to keep value of Controls between postbacks using Session

I have an ASP.NET Web Forms application. I am implementing a search functionality. I use a Master Page.
I would like to keep the value of the filters (two Textboxes, one DropDown and one CheckBox) between searches.
When I click the btnSearch button, Page_Load fires. If IsPostBack I load the Session with a Dictionary object (string control.ID, string control.Value) and then I have to assign this values to my controls again.
What is the best place to perform this assignment? The btnSearch_Click event handler? The Page_LoadComplete?









When the user press the search button btnSearch, the search is executed and the values of the controls MUST be kept.
When I press the butt ...