Let me talk about the situation first. At that time, I was debugging a new project. After I restored its corresponding database, when I ran the project, I reported this error ( other projects on this computer can run ) .
Then when I checked the Web.config of this new project, I found that the Data Source that it connected to the database was the IP address of the previous server.
It was like this before
<add key="数据库名" value="Date Source=之前服务器的IP地址; Initial Catalog=数据库名; User ..."/>
Change it to this, just use local
<add key="数据库名" value="Date Source=.; Initial Catalog=数据库名; User ..."/>