Dropdownlist

 Hi

II don't understand something with the  DropDownList
If I do abinding as the following
             DropDownList1.DataSource = dr;
            DropDownList1.DataTextField = "CategoryName";
            DropDownList1.DataValueField = "CategoryId";    Id is a OleDbType.Integer in the database
            DropDownList1.DataBind();
            cnx.Close();

        }
    }
If I want to retrieve the CategoryId selected
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
  & ...