Building a C++ style web server app in C#?

chroniclemaster1 · June 29th, 2010, 04:15 PM

My understanding is that programming with webforms like I am now sends the request through any and all of the application's HttpModules, then routes the request through an HttpHandler (possibly a custom .ashx) and a text file (the .aspx page) in order to generate a response. Any correction on this would be appreciated if I'm wrong.

I would like to play with a concept I've heard the C++ guys do, just using C#. Can I simply grab the HttpRequest and build the HttpResponse directly, maybe using an HTTP Module or MVC??? I'd like to experiment taking a request for a URL like http://www.myapp.com/subfolder/subfolder2/thispage.aspx, parse the URL and HTTP headers for input, draw in application logic code and database data, and construct the HTTP response without ever having a physical file "thispage.aspx" sitting in subfolder2.

Imar · June 29th, 2010, 04:26 PM

Hi there,

You need to write an HTTP handler (IHttpHandler) and map it to your URL / extension. Here's a random tutorial http://www.brainbell.com/tutorials/A...tpHandler.html but many more exist,

For the record: the "text file" is more or less coincidence. It's actually an IHttpHandler (the Page class) that is responsible for processing the request.

Cheers,

Imar

chroniclemaster1 · July 1st, 2010, 04:41 PM

Yes! Thank you very much.

I'm working up a test page, and I think it would make the most sense to keep the convention of the .aspx extension. I see no reason to change it, and since the beta site is on shared hosting, I don't think I'm allowed to remap any extensions in IIS anyway. However, this looks like it would break all my existing pages. If my pseudocode looks like this...

Code:

Retrieve URL of request

Search for URL in DB

if the URL exists in the DB (ie it's my new test)
     // DO STUFF

else
     // attempt to serve the old page normally

My decision-making code will short circuit the normal process so I can play around, but how do I code the ELSE so that every other page on my website doesn't die?

Imar · July 2nd, 2010, 02:52 AM

You don't have to remap URLs in IIS, you can remap them in web.config. For example, you can create an HTTP Handler (.ashx extension) with this code:

Code:

 
public class MyHandler : IHttpHandler
{
  public void ProcessRequest(HttpContext context)
  {
    context.Response.ContentType = "text/plain";
    context.Response.Write("Hello World");
  }
 
  public bool IsReusable
  {
    get
    {
      return false;
    }
  }
}

You can then remap existing URLs to this new handler in web.config:

Code:

 
<urlMappings enabled="true">
  <add url="~/SomeUrl.aspx" mappedUrl="~/MyHandler.ashx"/>
</urlMappings>

So, I would only remap the exceptions to your own HttpHandler and not all extensions which then requires you to try and find out what your code can handle and then give the rest back to the framework.

Alternatively, if you still want to do it from your own handler (not recommended), you can do something like this in ProcessRequest of the IHttpHandler:

Code:

 
if (someCondition)
{
  string virtualPath = "~/Default.aspx";
  string physicalPath = context.Server.MapPath(virtualPath);
  IHttpHandler handler = PageParser.GetCompiledPageInstance(virtualPath, physicalPath, context);
  handler.ProcessRequest(context);
  context.ApplicationInstance.CompleteRequest();
}

Be aware of a few issues though: first: this new ProcessRequest will probably trigger your handler again which will call ProcessRequest which will trigger your handler which will call , well, I think you get the idea. You need to code some stuff to avoid that.

Also, not 100%, but there might be some issues with regard to caching when you execute pages like this. You may want to read up on IHttpHandler and IHttpHandlerFactory if you continue down this path.

Cheers,

Imar