Ok, now this is VERY frustrating. When working in Visual Studio 2005 (and supposedly 2003 from this article http://blogs.msdn.com/webdevtools/archive/2007/09/17/tip-trick-asp-net-mobile-development-with-visual-studio-2008.aspx, but I do not remember, it has been to long) there was a template to choose from when adding a new item to a project called "Mobile Web Form" as shown below:
When I was working in Visual Studio 2008 Beta 2, I found the same template and it worked just like Visual Studio 2005. Once Visual Studio 2008 RTM'd in November, I installed it. A couple of days ago, I was showing my boss at work how to add a mobile page and while saying "Yeah, you must add a new item to your project like so...", neither one of us could find it. I felt like an idiot. It looks like the "Mobile [WebForm|Web Configuration File|Web User Control]" templates were removed in the RTM version! Others have confirmed this.
I find this quite irritating and annoying. Yes, its true, you can create a regular Web Form and then change the Inherits attribute in the <%@ Page %> directive, to make it MobilePage (assuming you brought in the System.Web.Mobile.dll reference). But, then I noticed that switching to design view instead of source view, the designer says it does not support designing mobile web forms.
WTF! I sure hope Microsoft ships a hot fix or includes this support VERY soon, in an update. I wonder if they needed to take that out to meet the RTM date they set? You can't take a feature out when it was in 2 previous versions like this Microsoft. In addition, the Expression based designer integrated in to VS2008 is a little quirky when your doing custom control development and you have [DesignerSerializationVisibility(DesignerSerializationVisiblitly.Content)] attribute on some properties. Sometimes, for whatever reason, instead of serializing the control properties to the page, it puts in a BUNCH of literals to replace the content with...but you still shipped it Microsoft.