Using WCF In An XBAP
Steve Maine confirmed to Rob and me that Windows Communication Foundation (WCF, codename "Indigo") will work in partial trust in upcoming .NET Framework v3.5. This means you can now use HTTP binding in WCF from within a XAML Browser Application (XBAP).
What does this mean? Well, using WCF you will now get parity for things for which you have been using ASMX within your XBAP. Secure communication is possible via transport layer security only.
Not all WCF features are available from within an XBAP though. This means you cannot currently host services, have duplex communications, use non-HTTP transports, or use WS-* protocols. Please use the WCF Forum or the WPF Forum to tells us what you think. We'd love to hear your feedback on this feature.
For the differences between ASMX 2.0 and WCF, see this article. If you already have ASMX services for which you were using an ASMX client, here's how to migrate ASMX to WCF. I should add, you are already able to access a WCF service using an ASMX client.