private void rating_Click(object sender, EventArgs e)
        {
            DataBaseAccess database = new DataBaseAccess();

            database.StartConnection();

            // if already added a rating then change it
            if (database.UserRatedAsset((int)_curUserData.GetUserID(), _userAsset.GetID()))
            {
                int ratingId = -1;

                List <Classes.UserRating> ratingsOfAsset = database.GetRatingsOfAsset(_userAsset.GetID());

                // get the rating id of the previous rating
                for (int i = 0; i < ratingsOfAsset.Count; i++)
                {
                    if (ratingsOfAsset[i].ReviewerID == _curUserData.GetUserID())
                    {
                        ratingId = ratingsOfAsset[i].ID;
                        break;
                    }
                }

                if (ratingId != -1)
                {
                    database.ChangeRatingStars(ratingId, starRating._rating);
                }
            }
            // if not rated yet then add rating
            else
            {
                database.AddRating((int)_curUserData.GetUserID(), _userAsset.GetID(), starRating._rating, "");
            }

            updateOverallRating(sender, e);
            database.CloseConnection();
        }