Config

<configuration>
    
    <connectionStrings>
        <add name="db_userConnectionString" connectionString="Data Source=WWW-C21CD4737E0;Initial Catalog=db_user;Integrated Security=True"
            providerName="System.Data.SqlClient" />
    </connectionStrings>
    
    <system.web>
        <compilation debug="true" targetFramework="4.0" />
    </system.web>

</configuration>

   <connectionStrings>
        <add name="db_userConnectionString" connectionString="Data Source=WWW-C21CD4737E0;Initial Catalog=db_user;Integrated Security=True"
            providerName="System.Data.SqlClient" />
        <!-- 简化 <add name ="123" connectionString =""/>
        
         另一种方法
     <appSettings>
        <add key="aa" value="Data Source=WWW-C21CD4737E0;Initial Catalog=db_user;Integrated Security=True"/>
        </appSettings>-->
    </connectionStrings>

前台调用 ： 加 using System.Configuration;

eg: string str = ConfigurationManager.ConnectionStrings["db_userConnectionString"].ToString();