private void btnSearch_Click(object sender, EventArgs e)
 {
     string key = this.txtSearch.Text;
     string catalog = "";
     if (key == "".Trim())
     {
         MessageBox.Show("Please enter keyword!", "Notice");
         return;
     }
     if (this.cboSearch.Text == "Book Title Status")
     {
         catalog = "matinhtrang";
     }
     else if (this.cboSearch.Text == "Publisher")
     {
         catalog = "manxb";
     }
     else if (this.cboSearch.Text == "Type Of Book")
     {
         catalog = "matheloai";
     }
     else if (this.cboSearch.Text == "Name")
     {
         catalog = "tensach";
     }
     else if (this.cboSearch.Text == "Summary")
     {
         catalog = "tomtat";
     }
     BookTitleBLL bookTitleBLL = new BookTitleBLL();
     List<BookTitleBLL> bookTitleList = new List<BookTitleBLL>();
     bookTitleList = bookTitleBLL.search(catalog, key);
     this.dgvBookTitle.Rows.Clear();
     if (bookTitleList != null)
     {
         foreach (BookTitleBLL row in bookTitleList)
         {
             this.dgvBookTitle.Rows.Add(row.BookTitleId, row.BookTitleStatusId, row.PublisherId, row.TypeOfBookId, row.Name, row.Summary);
         }
     }
     this.GetSelectedValueDataGridViewBookTitle();
     this.dgvBookTitle.SelectionChanged += new EventHandler(dgvBookTitle_SelectionChanged);
 }