Creating an extensible properties class (OOP)

I have an application which supports multiple types and versions of some devices. It can connect to these devices and retrieve various information. Depending on the type of the device, I have (among other things) a class which can contain various properties. Some properties are common to all devices, some are unique to a particular device. This data is serialized to xml. What would be a preferred way to implement a class which would support future properties in future versions of these devices, as well as be backwards compatible with previous application versions? I can think of several ways, but I find none of them great: - Use a collection of name-value pairs: - pros: good backward compatibility (both xml and previous versions of my app) and extensibility, - cons: no type safety, no intellisense, requires implementation of custom xml serialization (to handle different `value` objects) - Create derived properties class for each new device: - pros: type safety - cons: have to use `XmlInclude` or custom serialization to deserialize derived classes, no backward compatibility with previous xml schema (although by implementing custom serialization I could skip unknown properties?), requires casting for accessing properties in derived classes. - Another way to do it? I am using C#, by the way.