HTTP Module Events

There’s a fair number of events you can listen for in a .NET HTTP Module. I forget most of them and certainly their order – here’s a reminder.

These events are listed in sequential order:

• BeginRequest: Request has been started. If you need to do something at the beginning of a request (for example, display advertisement banners at the top of each page), synchronize this event.
• AuthenticateRequest: If you want to plug in your own custom authentication scheme (for example, look up a user against a database to validate the password), build a module that synchronizes this event and authenticates the user how you want to.
• AuthorizeRequest: This event is used internally to implement authorization mechanisms (for example, to store your access control lists (ACLs) in a database rather than in the file system). Although you can override this event, there are not many good reasons to do so.
• ResolveRequestCache: This event determines if a page can be served from the Output cache. If you want to write your own caching module (for example, build a file-based cache rather than a memory cache), synchronize this event to determine whether to serve the page from the cache.
• AcquireRequestState: Session state is retrieved from the state store. If you want to build your own state management module, synchronize this event to grab the Session state from your state store.
• PreRequestHandlerExecute: This event occurs before the HTTP handler is executed.
• PostRequestHandlerExecute: This event occurs after the HTTP handler is executed.
• ReleaseRequestState: Session state is stored back in the state store. If you are building a custom session state module, you must store your state back in your state store.
• UpdateRequestCache: This event writes output back to the Output cache. If you are building a custom cache module, you write the output back to your cache.
• EndRequest: Request has been completed. You may want to build a debugging module that gathers information throughout the request and then writes the information to the page.

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Tags: .NET, HTTP Module, IIS Pipeline