Will WCF allow me to use object references across boundaries on objects that implement INotifyPropertyChanged or contain observablecollection objects?

Question

So I've created a series of objects that interact with a piece of hardware over a serial port. There is a thread running monitoring the serial port, and if the state of the hardware changes it updates properties in my objects. I'm using observable collections, and INotifyPropertyChanged.

I've built a UI in WPF and it works great, showing me real time updating when the hardware changes and allows me to send changes to the hardware as well by changing these properties using bindings.

What I'm hoping is that I can run the UI on a different machine than what the hardware is hooked up to without a lot of wiring up of events. Possibly even allow multiple UI's to connect to the same service and interact with this hardware.

So far I understand I'm going to need to create a WCF service. I'm trying to figure out if I'll be able to pass a reference to an object created at the service to the client leaving events intact. So that the UI will really just be bound to a remote object.

Am I moving the right direction with WCF?

Also I see tons of examples for WCF in C#, are there any good practical use examples in VB that might be along the lines of what I'm trying to do?

Answer 1

No, WCF is a message based system - you pass around serialized (text/xml) messages. There's no "object references" that you can pass around.

The client has a proxy, which gives you the ability to "call" the service method. The WCF runtime then captures the parameters to that call, packages them up in a serialized message, and sends that message across the wire.

There is no direct connection between the client and the server - the client can't "reach over" to the service to get a remote object, nor can the service go back to the client to find out who called it or anything like that.

All that you want to send to the service must be part of either the message itself, or the headers that accompany the message.

Those messages must conform to the XML schema standard, which again means: only concrete non-generic types. You can't pass around interfaces, you cannot pass references - only concrete types made up of basic types such a string, int, datetime etc.

Update: maybe you need to check out the publish/subscribe (pub/sub for short) pattern - which you can also build using WCF. This would allow you data collection machine to publish its data on a regular basis or whenver it changes, and any number of subscribers could be notified of those changes.

Check out some of those articles - googling or binging for "WCF pub sub" will definitely turn out quite a few more!

• Tom Hollander: Building a Pub/Sub Message Bus with WCF and MSMQ
• Pub/sub sample with WCF net.tcp protocol in Silverlight 4
• Pub/sub sample using HTTP polling duplex WCF channel in Microsoft Silverlight 3
• WCF Router and Publish/Subscribe Sample Implementation