Can you explain the life cycle of an HttpModule?

The life cycle of an HTTP module in ASP.NET involves several stages as the module participates in the request processing pipeline. Here's an overview of the typical life cycle of an HTTP module:

1. Initialization:
   • When the application starts, the 'Init' method of each registered HTTP module is called. This method is responsible for setting up the module and subscribing to relevant events in the pipeline.
   • Here's an example of an HTTP module with an 'Init' method:

     
     
     public class LoggingModule : IHttpModule
     {
         public void Init(HttpApplication context)
         {
             // Subscribe to events
             context.BeginRequest += OnBeginRequest;
             context.EndRequest += OnEndRequest;
         }
     
         // Other methods and event handlers
     }
     
     

     In this example, the 'Init' method is used to subscribe to the 'BeginRequest' and 'EndRequest' events.
2. Request Processing:
   • As requests arrive at the ASP.NET application, the module's event handlers are triggered at different stages of the pipeline.
   • In the example above, the 'OnBeginRequest' method would be executed when the 'BeginRequest' event occurs, allowing the module to perform custom logic at the beginning of request processing.
3. Custom Logic:
   • The module's event handlers are where you can write custom logic to modify the request or response.
   • For instance, in the 'OnBeginRequest' event handler, you might capture request information, perform logging, or modify headers.
   • Similarly, in the 'OnEndRequest' event handler, you can inspect the response, add additional content, or perform cleanup tasks.

     
     
     private void OnBeginRequest(object sender, EventArgs e)
     {
         // Custom logic for request processing
     }
     
     private void OnEndRequest(object sender, EventArgs e)
     {
         // Custom logic for response processing
     }
     
     

4. Completion and Cleanup
   • After the request processing is complete and the response has been sent to the client, the module's event handlers have finished executing.
   • At this point, the module's resources can be cleaned up or any necessary post-processing can be performed.
5. Disposal:
   • When the application is shutting down or the module is being removed, the Dispose method of the module is called.
   • The 'Dispose' method allows you to release any resources held by the module.

     
     
         public void Dispose()
         {
             // Cleanup resources
         }
     	
     

     It's important to implement proper disposal and cleanup logic within the 'Dispose' method

By implementing the 'Init', event handlers, and Dispose methods, you can control the behavior of the HTTP module throughout the request processing pipeline. The module's event handlers are triggered at specific stages, allowing you to customize and modify the request and response as needed.