I have a form as
When accessing in C# code-behind via
I also had the same issue recently, when posting the form action attribute would use the rewritten path, but I wanted to show the raw url. I don't have any url rewriting libraries installed.
I found this page was very useful in getting my postbacks to work: http://www.codeproject.com/Articles/94335/TIP-How-to-Handle-Form-Postbacks-when-Url-Rewritin