We're using .NET Remoting with a Client/Shared/Server architecture where:
Shared DLL: common to both Client and Server
Server EXE: implements Shared interfaces
Client EXE: creates proxies of Shared interfaces to access Server
Now, on the Client-side, we need to have some of the class objects editable via a PropertyGrid which will then be updated to Server.
Option A: mark the Shared classes with all the necessary System.ComponentModel attributes for PropertyGrid
Option B: use near 1:1 wrapper classes in Client and use System.ComponentModel attributes? (PITA because of code duplication)
Option C: ?
PropertyGrid looks at the object - it isn't really interested in interfaces (and explicit interface implementations won't even show in PropertyGid).
If you already have a view-model approach then obviously decorate the view-model.
It really comes down to how much separation you want. Since you are sharing the library it isn't beyond reason to decorate the underlying model; however, if you don't want the UI knowing about the underlying types, then add a view-model, perhaps with the view-model talking to the interfaces (so it doesn't care what the actual implementation is).