CODEWITHSUNDEEP
asp.net
sly_Chandan
sly_Chandan

Reputation: 3515

What is the difference between HttpApplication class and IHttpModule?

What is the difference between HttpApplication class and IHttpModule? Are they both same or different?

I see articles that mention the same events in both the classes.

Upvotes: 3

Views: 2699

Answers (4)

Robert Koritnik
Robert Koritnik

Reputation: 105081

HttpApplication is the web application instance that has multiple IHttpModule instances registered in it. That's why every IHttpModule instance handles a certain part of application execution thus can usually be reused on many applications (think of a Session handling module or authentication module).

In terms of application/request handling there are many similarities. HttpApplication has access to application-level events like OnStart, OnEnd etc as well as request-level events like OnBeginRequest, OnEndRequest etc. IHttpModule on the other hand only has access to request-level events.

Additional note: It's possible to handle application start and end events even using an IHttpModule, but this is a non-documented feature and you have to take some special precautions. Check these two blog posts that explain it all into great depth:
Writing a custom IHttpModule that handles Application_OnStart event
How to correctly use IHttpModule to handle Application_OnStart event

I suggest you read a bit about application life cycle execution pipeline:

Upvotes: 4

Matías Fidemraizer
Matías Fidemraizer

Reputation: 64943

IHttpModule is a managed request handler, which means that implements "catches" for the request life-cycle.

HttpApplication represents the Web server (IIS) ASP.NET application. Right, it has the events and other members that you need in the context of an HTTP Module.

You may develop a HTTP module if you need to implement a customized way of handling some input data given by some HTTP request. Obviously, that may require you to access the HTTP application, which is the one exposing the request life-cycle events.

The summary is HTTP module is an observer of HTTP application that may implement logic in order to process an HTTP request in the way the HTTP application signals every step of ASP.NET infraestructure life-cycle.

Upvotes: 0

immutabl
immutabl

Reputation: 6903

http://aspalliance.com/442_Introducing_HTTPModules.all

Good article that should help your understanding of how HttpModules and HttpApplications work together.

Upvotes: 0

davidsleeps
davidsleeps

Reputation: 9513

There isn't any great difference other than HttpModules allow you to remove or separate the handling of an event from the rest of your application. This can help with code reuse, particularly across applications.
Furthermore, using this technique you can add in HttpModules to your application without having to change any existing source code (e.g. Elmah) to provide extra functionality.

Upvotes: 0

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