While migrating a simple project from Silverlight 3.0 to 4.0 RC, I’ve noticed that the my project no longer compiles. I’ve started getting errors which said that something like “Array does not have an Add method”. After looking at the proxy that was generated by the add reference dialog, I’ve noticed that the ObservableCollection option is no longer available on the Service Reference Dialog (as you can see from the following image):
The good news is that this is a bug in the RC version and it should be fixed in the final release. Thank god for that!