Some important facts about -asp.net

Question:
Can I still run ASP pages on a server that runs ASP.Net?

Answer:
Yes. They will run side-by-side with no adverse affects to the ASP pages at all.

Question:
Does ASP.Net still recognize the global.asa file?

Answer:
ASP.Net does not recognize the standard ASP global.asa file. Instead it uses a file named global.asax with the same – plus additional – functionality.

Question:
Can ASP pages and ASP.Net pages share session variables.

Answer:
No. Both support session variables, but the session variables are not shared across the two platforms.

Question:
What is the process-flow for ASP.Net?

Answer:

1. User requests an ASPx page in their browser

2. An HTTP requests is sent to IIS

3. The xspisapi.dll isapi filter intercepts the request and passes the request on to the XSP worker process (xspwp.exe)

4. Xspwp takes care of handing the request to the appropriate HTTPModules and finally an HTTPHandler as defined in the configuration files.

5. The ASPX page is read from the HD or cache and server code is loaded into memory and executed.

6. The server side code outputs normal HTML which is handed back through the chain of modules and eventually to IIS, which sends the response back to the client’s browser.

7. If the user clicks or otherwise acts on an HTML element (say, a textbox) that has a server side event handler, the form is posted back to the server with hidden form fields containing information as to what control and event occurred.  Some controls do not automatically post by default, but wait for a button_click event to post.  This is configurable by the developer.

8. The ASPx page is again loaded into memory using the same sequence of events as before, but this time ASP.net reads in the hidden form field data and automagically triggers the appropriate _OnChange, OnClick and other appropriate event handlers.

9. Resulting HTML is sent to the browser

10. The process continues in a continual "Post Back" cycle.

Definition of HTTP Modules:
HTTP modules are a logical replacement for ISAPI filters.  Modules are a class that can participate in every web request.  This is appropriate for code that should run on every request, such as caching, authentication or state management

Definition of HTTP Handlers:
HTTP Handlers provide the end point in the processing of a web request and are equivalent to ISAPI Extensions today.  For example, many handlers can be involved in the request for an ASPX page, but only 1 handler is invoked.  The handler runs after the HTTP modules have run.  Which handler is invoked is determined by configuration settings in the config.web file.  Handlers are assigned to handle requests based on the extension of the page requested.