Coolite 

You have 2 options. It'll post back to the same page if you don't specify PostURL (think of it as setting a form's action attribute). If you use the provided HTTPModule (see the web.config), you can specify ProcessorType and provide a class that implements the IFileUploadProcessor interface or extends AbstractFileUploadProcessor. See the Default.aspx.cs file for more details.

Using the HTTPModule is preferred because it allows you to intercept the request and not buffer the file in memory before storing it. Just add the following to the system.web/httpModules/ node:

<add name="FileUploadModule" type="ServerControls.FileUploadModule, ServerControls"/>

Yeah, I think I know exactly why. That class is instantiated and run in an HttpModule before the session information is loaded on a postback. I didn't think about sessions because our app requires sessionless connections.

I do have a couple of fixes I've been meaning to upload -- but until the session issue has been fixed, you can always use .AdditionalPostParameters() and pass in whatever you might need.

We use it to pass in the user's ID so we know who to associate the file with.

The reason I wrote the HTTP module was to get at the file being uploaded before it was cached in memory. I'll look into it.

I could still really use some help with the design-time portion of it.

It could be a trust issue - it does use reflection. I don't have much experience in the shared hosting arena and running websites in partial trust environments. I usually have full control of the site and therefore never any permissions problems.

I'm hoping there's someone out there who could lend a hand with this problem?

I suppose debugging on the server would be difficult - but you could add a bunch of debug statements and output to a file to see if your handler is being called. You could ad-hoc your way into finding out where the code is dying. Once you find that, I might be able to be of more assistance.

In summary, insert debug statements throughout the code until you're able to pinpoint where it's dying. Then let me know the class, method name, and line where it's failing along with any pertinent information.