I've been watching the Silverlight forums since the release of Silverlight 2, and I've noticed folks are having problems getting their Silverlight 2-based apps to work with Web services. There have been a number of API changes between Silverlight 1.2 and 2, including the removal of the BrowserHttpWebRequest class and related APIs and the addition of HttpWebRequest, HttpWebResponse and supporting classes. Silverlight 2 offers built-in support for asynchrous Web services calls only. In addition, the Web services proxy support has changed from ASP.NET style proxies to WCF proxies. On top of this, cross-domain issues are tripping up some folks. Silverlight-based apps can only call services hosted in the same domain, or services that have a cross-domain permission in place.
I've got a couple of tips to offer and I can point you to some great blog posts on the subject. First the tips:
Finally, there are some great blog posts that go into more detail about some of the items I've touched on. Check out Tim Heuer's post that discusses how to call ASP.NET, WCF and REST services from Silverlight and Pete Brown's post, which delves into WCF and Silverlight integration; including an explanation of the service binding requirements and more details about how to allow cross-domain calls from your service.