错误消息告诉您 非常明确 您必须做些什么才能找出问题所在.

您所要做的就是按照给出的说明进行操作(使用简单的英语，并附带一个示例)，错误将在所有的荣耀中显示.
在此之前，您或我们无法采取任何措施来解决问题.

The error message tells you very explicitly what you have to do to find out what the problem is.

All you have to do is follow the instructions given (which are in plain English, with an example) and the error will be displayed in all it''s glory.
Until then, nothing you or we can do will help to fix the problem.

我自己解决了这个问题，但实际上我忘记了打开连接，因此出现此错误，谢谢您.

I solve it myself actually I forget to open connection, so I get this error thank you.

打开您的Web.config文件
并在<system.web></system.web>中定义如下

Open your Web.config file
and in <system.web></system.web> define like following

<system.web><br />
        <customerrors mode="Off" /><br />
</system.web>

谢谢

Thanks