private void textBox9_TextChanged_1(object sender, EventArgs e)
        {
            String circuBookNo = textBox9.Text;

            textBox11.Text   = "";
            textBox10.Text   = "";
            label7.Text      = "";
            label7.ForeColor = Color.Red;
            bookBorrowAble   = false;
            checkBorrowAble();
            if (circuBookNo.Length == 10)
            {
                try
                {
                    CircuBookClass book = BookInfo.queryABookInfo(circuBookNo);
                    textBox11.Text = book.BookName;
                    textBox10.Text = book.PublishingHouse;
                }
                catch (System.ArgumentOutOfRangeException)
                {
                    label7.Text = "图书标识号有误!";
                    return;
                }
                if (!AS.BookBorrowAble(textBox9.Text))
                {
                    label7.Text = "书籍已被借出!";
                }
                else
                {
                    label7.ForeColor = Color.Green;
                    label7.Text      = "该书籍可借阅";
                    bookBorrowAble   = true;
                    checkBorrowAble();
                }
            }
        }