Today's Web Service Stack: ASMX 2.0 + WSE 3.0

When you see how ASMX 2.0 and WSE 3.0 are coming together, it creates hope for Web service developers in the trenches today, especially those who will not have the luxury of moving to WCF immediately. That was the vibe during my PDC precon -- one of hope, encouragement, and excitement. It was a refreshing change. Instead of getting the usual complaints about "why doesn't it do this?" or "why not that?" it was "wow, so you're telling me I have most of what Indigo provides and it's ready today?" There are a few attendee summaries of the workshop here and here.

 

Obviously ASMX2 + WSE3 doesn't match up to Indigo's full architecture and feature set, but it does give you some of the key features and the best feature is that it's available today (almost). 

 

For example, it gives you a similar programming model (via ASMX), which includes support for decoupling the service contract from the implementation by annotating interfaces, a similar application hosting model (via SoapReceivers), similar transport support (mainly HTTP, TCP, and IPC), and a similar support for message-based security. Those seem to be the big nuggets that most developers care about anyway. The main things WCF gives you that ASMX + WSE don't are the additional WS-* protocol implementations, more transport & encoding choices, and more service behavior knobs. I did a quick braindump of the main differences that come to mind:

 

Feature	ASMX2 + WSE3	WCF ("Indigo")
Hosting	IIS/ASP.NET (.asmx) SoapReceivers	IIS/ASP.NET (.svc) ServiceHost<T> WAS
Programming Model	[WebService], [WebMethod], etc. in System.Web.Services System.Web.Services.Protocols (supports interfaces, generics, etc)	[ServiceContract], [OperationContract], etc. in System.ServiceModel (supports interfaces, generics, etc)
Message Exchange Patterns (MEP)	One-way Request-response Custom (using WSE API)	One-way Request-response First/last-operation Duplex Custom
XML Serialization	System.Xml.Serialization	[DataContract] and friends System.Xml.Serialization (you can choose which to use)
Encodings	XML 1.0 MTOM	XML 1.0 MTOM Binary Custom
Transports	HTTP TCP Named pipes	HTTP TCP Named pipes MSMQ P2P Custom
Protocols	Security	Security Reliable messaging Transactions
Behaviors	Local transactions Buffering Caching Metadata customization Sessions Custom (via SoapExtensions and WSE filters)	Concurrency Instancing Throttling Thread-Binding Faults Exceptions Metadata customization Instance Pooling and JITA Impersonation Protection Authorization AutoEnlist Isolation AutoComplete Custom (via custom behavior types)

 

The big question in most developers mind is how soon they'll be able to move to WCF. The sooner, the better for most. However, thanks to the similarities shown above, you can build with ASMX2 + WSE3 today and get some immediate WCF-like benefits while feeling confident about your future migration path.