1. Modify configuration files, such as Machine.Config, Web.Config, Global.asax
2. Modified the bin directory and its contents
3. The number of recompilations exceeds the value set by <compilation numRecompilesBeforeAppRestart=/> in machine.config or web.config
4. Modify the physical path of the application virtual directory
5. Modify CAS policy
6. Restart the web service
7. Delete the subdirectory of the application (.net 2.0 only).
For AppDomain recycling, please refer to this blog post by Tess: http://blogs.msdn.com/tess/archive/2006/08/02/686373 .aspx