解决方式：
<appSettings>
<add key="MM_CONNECTION_STRING_myconn" value="Provider=Microsoft.Jet.OLEDB.4.0;Persist
Security Info=False; Data Source="/>
<add key="data" value="路径/XX.mdb" />
</appSettings>
调用语句
ConnectionString='<%#
System.Configuration.ConfigurationSettings.AppSettings["MM_CONNECTION_STRING_myconn"] +
Server.MapPath(System.Configuration.ConfigurationSettings.AppSettings["data"])%>'
