Question

It is just magic that I put some file in my site’s Bin folder and place a svc file to point to some assembly pointing to my service type. And then, I could magically Add Service Reference to the url like this:

http://www.myserver.com//xxx.svc

I really want to know how what happens from my click “Add Service Reference” to the proxy is generated properly. What does the IIS do during this period?

Answer 1

It’s not really magic – it’s metadata exchange ! 🙂

When you do a Add Service Reference in Visual Studio, behind the scenes, that service endpoint specified by the svc file is interrogated for its metadata. This is basically similar to a WSDL (Web Service Description Language) file – a machine-readable description of your service, its methods, what parameters they expect etc. – and a XSD (XML schema) that – again in machine-readable form – defines the parameter types used.

Based on those two pieces of information, the WCF client side import can create C# or VB.NET classes that

• mirror the exact service implementation on the service side – same method names, same parameters expected and returned
• create the necessary data classes – again in C# or VB.NET – based off of the XML schema file

So in the end – it’s really not magic. It’s the beauty of self-describing services and a bit of code generation that reads that metadata and creates client-side proxy classes from that metadata description

If you’re interested in more details about metadata, read the MSDN docs on WCF metadata – quite extensive and in-depth.