First up, great to see so many of you at the session on Tuesday, thanks for making the time etc!!
I was asked to post up the sample code, but tbh, I don't think this makes a lot of sense now as re have released the beta under it's new name of .NET RIA Services. Also some of the controls that were part of Alexandria are now included in SL3, notably DataForm and DataPager, so it's unlike the code I have will work as is.
That said there is a great set of learning resources at http://silverlight.net/learn/labs.aspx
Check out this Tim's excellent summary of what is new in Silverlight 3, he's done a great job in pulling together the resources and references for SL3, see http://timheuer.com/blog/archive/2009/03/18/silverlight-3-whats-new-a-guide.aspx
I've put the slides up at http://cid-d03fa499b14904f9.skydrive.live.com/browse.aspx/Presentations
A great question was asked with about Roles Based Navigation
A question was asked if it was possible for the navigation framework to operate in a similar fashion to ASP.NET Sitemaps, exposing navigation links based on the roles the authenticated user belongs as per ASP.NET sitemaps and Security Trimming. For now this is not a part of the .NET RIA Services Framework, but is something that is under consideration.
Also given a brief discussion on the CSLA Framework - then check out http://www.lhotka.net/weblog/OverviewOfCSLANET36ForWindowsAndSilverlight.aspx