I really love developing on ASP.NET with C# and will definitely continue using this technique from Microsoft. But everything can not be perfect. The greatest shortcoming of the framework is to me that there isn't any good native support for URL-rewriting. I have written a bit about it before.
It's especially in the IIS 6 web server that the limitations exists. In the newer IIS 7 that will be released together with the Longhorn server there will be better solutions to create rules for URL rewrites. But there are some time left until this system will be released, so that doesn't help us right now.
What you can do at the moment is to use ASAPI-filters but that postulates that you are running your own dedicated server or are on a web host that will install it for you. Jeff Atwood at Coding Horror writes more about the two most common ASAPI-solutions for IIS.
One of the greatest critics of the situation is probably Mike Schinkel. This is the guy that started the wiki.welldesignedurls.org and the companion blog which contains a lot of great resources on the subject.
On his personal blog Mike is not holding back on the critizism. In a recent post with the headline "IIS 7.0: Too Little, Too Late?"another Mike (Program Manager för Microsofts IIS team) enters the discussion and is expressing his regrets over the bad situation.
I think it's really good that a lot of developers pays attention to the problem. Microsoft tells us that IIS 7 will not be available for Windows 2003 and that's a real pity. The new techniques are to deep related to the Longhorn system that are saying.
But who knows, after all this begging from developers perhaps Microsoft can spare some resources on it. I would be absolutely wonderful. My tip is to try to do a simpler upgrade to IIS 6 and try to make an implementation of the same URL-rewrite as in the upcoming web server. Name it something like IIS 6.5.
Some time ago I wrote about how to do URL rewrite with ASP.NET (and about the problems that are involved). Many developers has tried to tackle the problem and I will not go to ddep into the technical stuff this time. I will how ever save a few new links I found on the subject.
My conclusion is that it's probably smartest to wait until IIS 7 is released. Unfortunatly it doen't seems like we will get this web server for Windows 2003. We will probably have to wait for the new Longhorn server.
Several people have asked why the built-in URL Mapper in ASP.NET 2.0 doesn't support regular expressions. There were actually a few reasons for this -- one of the big ones being that just about the time we were about to consider adding it my team started also working on IIS7. We realized that a full-featured version would want/need to take advantage of some of the new features in IIS7 as well as the support all content types (in particular -- images and directories). So we postponed making it feature rich until a future version.
The question is if one really can wait. To have nicely formatted URLs is really tempting, especially from an SEO-perspective. But if you are going to use one of this tecniques just bear in mind that you might have to redo everything once IIS 7 is released.
If you want to have some thought from someone who has started using URL-rewrite with IIS 7 on Vista, you can read Dennis blog.