protected void txtNum_TextChanged(object sender, EventArgs e) { int quantity = 0; if (int.TryParse(((TextBox)sender).Text, out quantity)) { BookOrderModel book = new BookOrderModel(); TextBox textBox = (TextBox)sender; book.book.id = int.Parse(((TextBox)sender).Attributes["bookid"]); book.quantity = quantity; CartBLL.SetBookCount(GetCart(), book); } DataRebind(); return; }