Not sure if this is what you are looking for but what I am guessing is you want an event for your drop down list to get the info and place it into a session to pass onto the next page
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
string item=DropDownList.SelectedItem;
Session["selectedItem"]=item;
Response.Redirect("TheNextPageURL")
}
public partial class TheNextPage : Page
{
protected void Page_Load(object sender, EventArgs e)
{
if(Session["selectedItem"]!=null)
{
Label1.Text=Session["selectedItem"].toString();
}
}
}
Hope that helps