I just got word that Independentsoft has come out with a beta version of an EWS client API for the .NET Framework and .NET Compact Framework. I’ve not looked at it yet, but I’m particularly hopeful about having a good way to work with EWS from Windows Mobile devices.
Exchange Web Services (EWS), introduced in Exchange 2007 and enhanced in Exchange 2007 SP1, is Microsoft preferred interface for all future programmatic reach into the Exchange store. While EWS is a Web service, it can be pretty complicated to work with. Luckily, we’ve done some work with EWS here at 3Sharp; Paul’s been presenting some developer training sessions on EWS in partnership with Microsoft. We’ve found that Inside Microsoft Exchange Server 2007 Web Services has been a valuable reference on EWS.
One of the challenges for EWS development is that the schema and object model is pretty complex when compared with the typical Web service, enough so that you need to use special Visual Studio proxy classes when you use .NET to work with EWS. This, by the way, is very likely the cause of the compatibility issue I found between EWS and SharePoint Designer — Designer’s proxy classes aren’t the EWS-aware ones.