网络已断开连接，这意味着当用户执行操作然后断开连接时，您的代码就会运行。每次单击按钮时，您都需要打开与数据库的连接（该按钮会导致回发。）

The web is disconnected meaning your code runs when the user does something and then it disconnects. You'll need to open the connection to your db each time a button is clicked (the button causes a postback.)