getting error ; expected

i am getting this statement underlined saying ;expected,when i add this  code "(Cuo = Session["office"].ToString())" into the statement.
i tried alot but culdnt solve it
here is the code i have written so far
SqlCommand cm = new SqlCommand("SELECT Dec, Id, Year, Cuo FROM Departure WHERE (Year = Datetime.Now.Year) AND (Cuo = Session["office"].ToString()) AND (Dec = '" + ddl3.SelectedItem.ToString() + "'", con);