ASP.NET Impersonation （only your application code runs under the context of the impersonated user.）

When impersonation is enabled, only your application code runs under the context of the impersonated user. Applications are compiled and configuration information is loaded using the identity of the ASP.NET process. For more information, see Configuring ASP.NET Process Identity. The compiled application is put in the Temporary ASP.NET files directory. The application identity that is being impersonated needs to have read/write access to this directory. The impersonated application identity also requires at least read access to the files in your application directory and subdirectories. For more information, see ASP.NET Required Access Control Lists (ACLs).