ms access database not updated

in my query ms access database not updated.

here is my code


           cn.Open();
         
           OleDbCommand cmd = new OleDbCommand("update GENERALBILLING set  due=@due where invoicenumber=@invoicenumber", cn);
         
           cmd.Parameters.AddWithValue("@due", due);
           cmd.Parameters.AddWithValue("@invoicenumber", invoicenumber);
           
           cmd.ExecuteNonQuery();
        
           cn.Close(); 





Here invoicenumber is auto increament primary key