ASP.NET 4.5 Architecture

Request Processing 

1. IIS gets the request
2. Looks up a script map extension and maps to aspnet_isapi.dll
3. Code hits the worker process (aspnet_wp.exe in IIS5 or w3wp.exe in IIS6)
4. .NET runtime is loaded
5. IsapiRuntime.ProcessRequest() called by non-managed code
6. IsapiWorkerRequest created once per request
7. HttpRuntime.ProcessRequest() called with Worker Request
8. HttpContext Object created by passing Worker Request as input
9. HttpApplication.GetApplicationInstance() called with Context to retrieve instance from pool
10. HttpApplication.Init() called to start pipeline event sequence and hook up modules and handlers
11. HttpApplicaton.ProcessRequest called to start processing
12. Pipeline events fire
13. Handlers are called and ProcessRequest method is fired
14. Control returns to pipeline and post request events fire