Getting posted values on other page

 Hi to all
I had a problem and here is my code
 
if (PreviousPage != null)
            {
                DropDownList pid = (DropDownList)PreviousPage.FindControl("DropDownList1");
                this.DropDownList1.SelectedIndex = pid.SelectedIndex;
                DropDownList qty = (DropDownList)PreviousPage.FindControl("DropDownList2");
                this.DropDownList2.SelectedIndex = qty.SelectedIndex;
            }
 
I have to get values from previous page and get selected index ...