Wednesday, March 3, 2010

Asp.Net – Creating a new custom HTTP Module

An HTTP Module is a .NET class that executes with each and every page request. You can use an HTTP Module to handle any of the HttpApplication events that you can handle in the Global.asax file.

You are already familiar with some of the HTTP Modules like
  • FormsAuthenticationModule handles the Forms authentication
  • WindowsAuthenticationModule handles the Windows authentication
  • SessionStateModule manages the session state of application
  • OutputCacheModule deals with output caching
  • ProfileModule used for interaction with user profiles

Each HTTP Module subscribes to one or more HttpApplication events. For example, when the HttpApplication object raises its AuthenticateRequest event, the FormsAuthenticationModule executes its code to authenticate the current user.

Below I have included a sample class which implements the IHttpModule interface

In the Init event I have created an EventHandler for the PostAuthorizeRequest event of Http Application

namespace AspNet
    public class CustomContentModule : IHttpModule
        public void Init(HttpApplication app)
            app.PostAuthorizeRequest += new EventHandler(SendRequest);
        public void SendRequest(Object sender, EventArgs e)
            HttpApplication app = (HttpApplication)sender;
            app.Response.Write("Hi content from HTTP Module
Pay my tax also !!!"

        public void Dispose() { }

You can use any of the following events of HTTP Application; the events are raised in the following order:

  1. BeginRequest
  2. AuthenticateRequest
  3. PostAuthenticateRequest
  4. AuthorizeRequest
  5. PostAuthorizeRequest
  6. ResolveRequestCache
  7. PostResolveRequestCache

      After the PostResolveRequestCache event and before the PostMapRequestHandler event, an event handler (which is a page that corresponds to the request URL) is created. When a server is running IIS 7.0 in Integrated mode and at least the .NET Framework version 3.0, the MapRequestHandler event is raised. When a server is running IIS 7.0 in Classic mode or an earlier version of IIS, this event cannot be handled.

  1. PostMapRequestHandler
  2. AcquireRequestState
  3. PostAcquireRequestState
  4.  PreRequestHandlerExecute

      The event handler is executed.

  1. PostRequestHandlerExecute
  2. ReleaseRequestState
  3. PostReleaseRequestState

      After the PostReleaseRequestState event is raised, any existing response filters will filter the output.

  1. UpdateRequestCache
  2. PostUpdateRequestCache
  3. LogRequest.

      This event is supported in IIS 7.0 Integrated mode and at least the .NET Framework 3.0
  1. PostLogRequest

      This event is supported IIS 7.0 Integrated mode and at least the .NET Framework 3.0
  1. EndRequest

After creating this class add the following entry in Web.config

                        <add name="CustomContentModule" type="AspNet.CustomContentModule"/>

When you excute any page in this application HTTP Runtime will add the content from the HTTP module created by us. You can build on this to create more complex scenarious like custom authitication, generation.processing of data based on the paraametr availalle in the Http Application objects etc.

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