Concepts and interaction between IIS and ASP.NET components can be confusing at times. Relationships amongst IIS application, virtual directory, application pool, application domain are confusing at best. Having researched a bit, I attempted to model the various concepts and their inter-relationships using the following UML class diagram. Concepts in Pink applies strictly to ASP.NET domain. Concepts in Blue are applicable to IIS domain. A point to note is that a VirtualDirectory (VD) can contain other VDs. If a composed/ sub VD is not configured as an Application, the VD is treated as a sub-directory of the composing/ parent Application. As such, all the resources may be shared (e.g. application, session information). If the composed/ sub VD is configured as a separate Application, the resources are not shared (even if the same ApplicationPool is in use!). The reason is that the resources are isolated based on the ApplicationDomain . To deal with request/ session/ DB timeout, the...
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