Serializing UniqueId

Why can't UniqueId be serialized?

Data contracts only have native support for a limited set of types. If you use a type that is not in this native set, then you'll get an exception that the data contract is invalid unless you decorate the type with attributes that explain how the type should be serialized. Adding attributes requires you to change the type, which means that there are going to be many types in the world that can't be used with data contracts. This includes types in the framework.

System.Xml.UniqueId is an example of a type that lacks native support in the data contract implementation. It doesn't mean that there's anything wrong with that type, just that it can't be used with the data contract serialization mechanism. Other serializers will still work with the UniqueId type. For instance, XmlDictionaryWriter has native support to turn a UniqueId into a string, so the UniqueId type can be used with XML serialization.

Next time: Service Contract Generation