private void shopButton_Click(object sender, EventArgs e)
        {
            if (listView1.Items.Count < 1)
            {
                MessageBox.Show("购物车里没有任何物品!");
            }
            float sumAmount = 0;

            foreach (ListViewItem item in this.listView1.Items)
            {
                float amount = float.Parse(item.SubItems[4].Text);
            }
            if (customer.Balance + customer.CustomerCreditLimit >= sumAmount)
            {
                DateTime datetime = DateTime.Now;
                int      orderId  = SqlManage.queryMaxOrderId() + 1;
                SqlManage.insertOrder(orderId, customer.CustomerId, datetime);
                foreach (ListViewItem item in this.listView1.Items)
                {
                    int    detailId = SqlManage.queryMaxDetailId() + 1;
                    int    goodsId  = Convert.ToInt32(item.SubItems[0].Text);
                    int    goodsNum = Convert.ToInt32(item.SubItems[3].Text);
                    float  amount   = float.Parse(item.SubItems[4].Text);
                    Detail detail   = new Detail(detailId, orderId, goodsId, goodsNum, amount, 0);
                    SqlManage.insertDetail(detail);
                }
                MessageBox.Show("下单成功!");
            }
            else
            {
                MessageBox.Show("已超出最大赊购限额!");
            }
        }