（OP不知道主题是什么......）
问题描述：
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["con"].ConnectionString); Object引用中的此行错误未设置为对象的实例。检索错误
i第一次靠asp .net。所以给我的asp.net教程参考的网站地址列表
This line error in Object reference not set to an instance of an object.. retrieve the error
i am first time leaning in asp .net. So given to me list of website address for tutorial reference of asp.NET
答
ConfigurationManager显然找不到web.config文件中的连接字符串了名为con。
来吧。如果你只学习了如何使用调试器的基础知识，这非常容易。
The ConfigurationManager apparently couldn't find a connection string in your web.config file that was named "con".
Come on. This is VERY EASY to figure out if you only learned the basics of how to use the debugger.