I\'ve been coming up with a lot of dead ends on this question. Supposedly, .NET 3.5 SP1 has Support for ADO.NET Entity Framework entities in WCF contracts. But when I look for
The "sharing interfaces and not type" tenet presupposes that you don't own both ends of the wire and/or you're writing a public-facing web service. WCF can be used (and is used) in contexts where this is decidedly not the case. Many enterprise n-tier architectures have a WCF-fronted application tier to facilitate load-balancing among other things. In these cases it is perfectly valid to share type and, in fact, is desired.