CapDemo.BL.QuestionBL.GetQuestionByCatalogue C# (CSharp) Méthode

        public List<Question> GetQuestionByCatalogue(Catalogue Catalogue)
        {
            List<Question> QuestionList = new List<Question>();
            string query = "SELECT q.Question_ID, q.Question_Title, q.Question_Name, q.Question_Type, c.Catalogue_Name"
                         + " FROM Question q "
                         + " INNER JOIN Catalogue c ON c.Catalogue_ID = q.Catalogue_ID"
                         + " WHERE q.Catalogue_ID='"+Catalogue.IDCatalogue+"'";
            DataTable dt = DA.SelectDatabase(query);
            int i=1;
            if (dt != null)
            {
                foreach (DataRow item in dt.Rows)
                {
                    Question Question = new Question();
                    Question.IDQuestion = Convert.ToInt32(item["Question_ID"]);
                    Question.QuestionTitle = item["Question_Title"].ToString();
                    Question.NameQuestion = item["Question_Name"].ToString();
                    Question.TypeQuestion = item["Question_Type"].ToString();
                    Question.NameCatalogue = item["Catalogue_Name"].ToString();
                    Question.Sequence = i;
                    QuestionList.Add(Question);
                    i++;
                }
            }
            return QuestionList;
        }

        //LOAD QUESTION
        public void LoadQuestion()
        {
            QuestionBL QuestionBL = new QuestionBL();
            Catalogue Cat = new Catalogue();
            Cat.IDCatalogue = IDCat;
            List<DO.Question> QuestionList;
            QuestionList = QuestionBL.GetQuestionByCatalogue(Cat);
            if (QuestionList != null)
                dgv_Question1.DataSource = QuestionList;

            dgv_Question1.Columns["IDCatalogue"].Visible = false;
            dgv_Question1.Columns["IDQuestion"].Visible = false;
            dgv_Question1.Columns["AnswerContent"].Visible = false;
            dgv_Question1.Columns["Catalogue"].Visible = false;
            dgv_Question1.Columns["Date"].Visible = false;

            dgv_Question1.Columns["Sequence"].HeaderText = "STT";
            dgv_Question1.Columns["QuestionTitle"].HeaderText = "Tên câu Hỏi";
            dgv_Question1.Columns["NameQuestion"].HeaderText = "Nội dung câu Hỏi";
            dgv_Question1.Columns["TypeQuestion"].HeaderText = "Loại Câu Hỏi";
            dgv_Question1.Columns["NameCatalogue"].HeaderText = "Tên Chủ Đề";

            dgv_Question1.Columns["Sequence"].AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCells;
            dgv_Question1.Columns["NameCatalogue"].AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCells;
            dgv_Question1.Columns["TypeQuestion"].AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCells;
            dgv_Question1.Columns["QuestionTitle"].AutoSizeMode = DataGridViewAutoSizeColumnMode.DisplayedCells;
        }