private void btnSave_Click(object sender, EventArgs e)
        {
            try
            {
                if (dgvBookList.Rows.Count > 0)
                {
                    BookDT = new DataTable();
                    BookDT.Columns.Add("BookCode");
                    BookDT.Columns.Add("BookName");
                    BookDT.Columns.Add("Author");
                    BookDT.Columns.Add("ISBN");
                    BookDT.Columns.Add("Category");

                    foreach (DataGridViewRow row in dgvBookList.Rows)
                    {
                        DataRow dr = BookDT.NewRow();
                        dr["BookCode"] = row.Cells[1].Value.ToString();
                        dr["BookName"] = row.Cells[2].Value.ToString();
                        dr["Author"]   = row.Cells[3].Value.ToString();
                        dr["ISBN"]     = row.Cells[4].Value.ToString();

                        string category = row.Cells[5].Value.ToString();
                        dr["Category"] = Category_DAO.getCategoryID(category);

                        BookDT.Rows.Add(dr);
                        dr = null;
                    }

                    if (BookDT.Rows.Count > 0)
                    {
                        if (Book_DAO.SaveNewBook(BookDT) > 0)
                        {
                            MessageBox.Show("Save Successfully.", "Save");
                            dgvBookList.DataSource = null;
                        }
                    }
                }
                else
                {
                    MessageBox.Show("No Data found to Save.");
                }
            }catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        //Generate Book Code
        private void GenerateBookCode()
        {
            int Code = Book_DAO.getBookCount() + dgvBookList.Rows.Count;

            txtBookCode.Text = string.Format("BK-" + "{0:00000}", ++Code);
        }