Url rewrite without redirect in ASP.NET - iis-6

Question

We have a CMS system that creates long URLs with many parameters. We would like to change the way they are presented, to make them more friendly.
Since we have many sites already built on this CMS, it's a little difficult to rewrite the CMS to create friendly urls (although it's a method we're considering, if no alternative is found), we we're looking for a method that when a user clicks on a long url, the url will change into a friendly one - in the browser - without using Response.Redirect().
In Wordpress such a method exists (I'm not sure whether it's done in code or in Apache), and I'm wondering if it could be done in ASP.NET 2.0 too.
Another thing to take into consideration is that the change between the urls has to be done by accessing the DB.
UPDATE: We're using IIS6

Answer 1

If you're using ii7 the easiest way to do this is to use the URL Rewrite Module According to that link you can
Define powerful rules to transform
complex URLs into simple and
consistent Web addresses
URL Rewrite allows Web administrators
to easily build powerful rules using
rewrite providers written in .NET,
regular expression pattern matching,
and wildcard mapping to examine
information in both URLs and other
HTTP headers and IIS server variables.
Rules can be written to generate URLs
that can be easier for users to
remember, simple for search engines to
index, and allow URLs to follow a
consistent and canonical host name
format. URL Rewrite further simplifies
the rule creation process with support
for content rewriting, rule templates,
rewrite maps, rule validation, and
import of existing mod_rewrite rules.
Otherwise you will have to use the techniques described by Andrew M or use Response.Redirect. In any case I'm fairly certain all of these methods result in a http 301 response. I mention this because its not clear why you don't want to do Response.Redirect. Is this a coding constraint?
Update
Since you're using IIS 6 you'll need to use another method for URL rewriting.
This Article from Scott Mitchell describes in detail how to do it.
Implementing URL Rewriting
URL rewriting can be implemented
either with ISAPI filters at the IIS
Web server level, or with either HTTP
modules or HTTP handlers at the
ASP.NET level. This article focuses on
implementing URL rewriting with
ASP.NET, so we won't be delving into
the specifics of implementing URL
rewriting with ISAPI filters. There
are, however, numerous third-party
ISAPI filters available for URL
rewriting, such as:
ISAPI Rewrite
IIS Rewrite
PageXChanger
And many others!
The article goes on to describe how to implement HTTP Modules or Handlers.
Peformance
A redirect response HTTP 301 usually only contains a small amount of data < 1K. So I would be surprised if it was noticeable.
For example the difference in the page load of these urls isn't noticible
"https://stackoverflow.com/q/4144940/119477"
"https://stackoverflow.com/questions/4144940/url-rewrite-without-redirect-in-asp-net"
(I have confirmed using ieHTTPHeaders that http 301 is what is used for the change in URL)
Page Rank
This is what google's webmaster central site has to say about 301.
If you need to change the URL of a
page as it is shown in search engine
results, we recommended that you use a
server-side 301 redirect. This is the
best way to ensure that users and
search engines are directed to the
correct page.

Answer 2

In response to extra comments, I think what you need to do is bite the bullet and modify the CMS to write the new links out into the pages. You've already said that you have normal URL rewriting which can translate the new URLs to old when they're incoming. If you were to also write out the new URLs in your markup then everything should simply work.
From an SEO point of view, if the pages your CMS produces have the old links, then that's what the search engines will see and index. There's nothing much you can do about that, javascript, redirect or otherwise. (although a permanent redirect would get you a little way there).
I also think that what you must have been seeing in Wordpres was probably a redirect. Without finding an example I can't be sure though. The thing to do would be to use Fiddler or another http debugger to see what happens when you follow one of these links.
For perfect SEO, once you've got the new URLs working outbound and inbound, what you'd want to do is decide that your new URLs are the definitive URLs. Make the old URLs do a redirect to the new URLs, and or use a canonical link tag back to the new URL from the old one.

Answer 3

I'm not certain what you're saying here, but basically a page the user is already reading contains an old, long, URL, and you'd like it to change to the new, short URL, dynamically on the client side, before the browser requests the page from the server?
The only way I think this coule be done would be to use Javascript to change the URL in response to onclick or document.ready, but it would be pointless. You'd need to know the new short url for the javascript to re-write to, and if you knew that, why not simply render that url into the link in the first place?
It sounds more like you want URL routing, as included in ASP.Net 4 and 3.5?
Standard URL rewriting modifies the incoming request object on the server, so the client browser submits the new URL, and the downstream page handlers see the old URL. I believe the routing things extend this concept to the outgoing response too, rewriting old urls in the response page into new URLs before they're sent to the client.
Scott Gu covers the subject here:
http://weblogs.asp.net/scottgu/archive/2009/10/13/url-routing-with-asp-net-4-web-forms-vs-2010-and-net-4-0-series.aspx
Scott Gu also has an older post on normal URL rewriting outlining several different ways to do it. Perhaps you could extend this concept by hooking into Application_PreSendRequestContent and manually modifying all the href values in the response stream, but I wouldn't fancy it myself.
http://weblogs.asp.net/scottgu/archive/2007/02/26/tip-trick-url-rewriting-with-asp-net.aspx