Options for upgrading ASP .Net extensions for CRM 2011

I like April. One reason is that it's the start of my MVP renewal cycle. After April 1st April I will either have been renewed, or not, and I feel less circumspect about making critical comments about decisions Microsoft have made. So, ASP .Net extensions with CRM 2011. Since the first release of CRM (CRM 1.0 or CRM 1.2 depending on your country), a major extension point for On-Premise CRM implementations was to develop ASP .Net extensions and deploy them within the CRM web site. Having a supported way to place these extensions within the CRM web site was important for several reasons:

1. To allow relative Urls in IFrames, ISV.Config and SiteMap. Main reasons for that are to cope with IFD environments where different domain names are provided for internal and external access, and to avoid configuration issues exporting/importing between environments
2. To allow single-sign on and impersonation, so the code could act on behalf of the CRM user, without needing to re-enter their credentials
3. To maintain the Site Origin (aka same site of origin). This is an important consideration as Internet Explorer security will only permit code interaction between pages if it considers that they are part of the same site. For example, the ability to pass data to a dialog using window.dialogArguments, or the ability to access objects on a calling window via window.opener both depend on the pages being in the same site

However, CRM 2011 puts significant restrictions on putting your ASP .Net extensions within the CRM web site. Essentially, the only supported option is to retain existing extensions that use the CRM 4 endpoint. So, what happens to the points above if you can't put your ASP .Net extensions in the CRM web site:

1. You'll have to use absolute Urls. This makes deployment between environments (e.g. from development to live) harder, as the Urls would have to changed. In small-scale environments this would be just a manual task, but in larger environments you may decide to build a process to automate this. Overall, I see this as a major annoyance, but not a major problem
2. Microsoft have put work into making single sign-on work across web sites. This depends on setting up Secure Token Services, which incurs some administrative and deployment overhead. There's an additional deployment overhead of setting up a new web site for the extensions, and configuring access to it. I've not tested this fully, but assuming it works as promised, this should resolve the single sign-on and impersonation issue
3. This is the big problem area. I don't think same site of origin can be maintained with the ASP .Net pages outside of the CRM web site, which effectively removes support for a common type of extension that was possible in all previous versions (Note, IE 8 has some settings that affect how Site Origin is applied, and this might help, but IE 7 is a supported browser for CRM 2011, so this cannot be a universal solution)

So, what can/should you do with your ASP .Net extensions that you wrote for CRM 4.0, or were intending to write. I see 3 main options:

1. Don't upgrade your code. ASP .Net code that uses the CRM 4 web service endpoint will still work in the ISV folder, and Microsoft have not said it is unsupported. This is the simplest option, but it means you need to maintain CRM 4 code, and you'll still have to address the issue when CRM 6 comes out. You could cross your fingers and hope that, in CRM 6, Microsoft reintroduce support for ASP .Net extensions within the CRM web site
2. Upgrade the code to use the CRM 2011 endpoint, and deploy it in a separate web-site from CRM. As stated above, this causes extra deployment overhead (which I consider is a significant overhead, which is often under-estimated), and you won't be able to use same site of origin, so you have to expect some limitations
3. Rewrite the code as web resources (Silverlight, or HTML with javascript). Microsoft have introduced quite a lot of integration points in CRM 2011 that makes this a powerful option. This has a major advantage that the resources are necessarily hosted within the CRM web site, and can be deployed as part of a CRM solution. However, these are client-side technologies and some extensions would need extra work to build (e.g. extensions that access a database on another server). My biggest problem though is the development effort required to rewrite code in substantially different technologies, and these are technologies that are not as mature as ASP .Net

Of these, I don't like any of the options. Numbers 2 and 3 would be necessary if you need to support CRM Online, but for On-Premise implementations there are some difficult decisions to make. Don't get me wrong, I appreciate that there are a lot of good things for developers in CRM 2011; web resources and the single sign-on across web-sites are very powerful and very welcome, and the only options for CRM Online, it's just a shame to lose some On-Premise options.

But to finish on a more positive note, another reason I like April is that this is a great month for ski touring.