Hi, this is probably only some conceptual problem, but I cannot seem to find the ideal solution. I'd like to create a Silverlight client application that uses WCF to control a third party application via some self written webservice. If there is more than one Silverlight client, all clients should be synchronized, i.e. parameter changes from one client should be propagated to all clients. I set up a very simple Silverlight GUI that manipulates parameters which are passed to the server (class inherits INotifyPropertyChanged): public double Height { get { return frameworkElement.Height; } set { if (frameworkElement.Height != value) { frameworkElement.Height = value; OnPropertyChanged("Height", value); } } } OnPropertyChanged is responsible for transferring data. The WCF service (duplex net.tcp) maintains a list of all clients and as soon as it receives a data packet (XElement with parameter change description) it forwards this very packet to all clients but the one the packet was received from. The client receives the package, but now I'm not sure, what's the best way to set the property internally. If I use "Height" (see above) a new change message would be generated and sent to all other clients a.s.o. Maybe I could use the data field (frameworkElement.Height) itself or a function - but I'm not sure whether there would arise problems with data binding later on. Also I don't want to simply copy parts of the code properties, to prevent bugs with redundant code. So what would you recommend? Thanks!