Recreating the application domain and recompiling pages takes time, therefore unforeseen application restarts should be investigated. The application domain is unloaded when one of the following occurs:
Modification of machine.config, web.config, or global.asax.
Modification of the application's bin directory or its contents.
When the number of compilations (ASPX, ASCX, or ASAX) exceeds the limit specified by
Modification of the physical path of a virtual directory.
Modification of the code-access security policy.
The Web service is restarted.