Although it’s been mentioned before here, it bears repeating that before you find yourself making a reference to the DataContractJsonSerializer, you ought to consider and indeed are more likely better off with the NewtonSoft library Json.NET. Whereas the DataContractJsonSerializer relies on giving you the flexibility of creating types and using the DataContract and DataMember attributes on them for a lot of granular control, this is burdensome with types that should naturally find themselves serializable and JSON friendly. For example, let’s say I have a Dictionary<int, string>; the intent of the user shouldn’t be too complicated in the serialization process. Or, if I have a class Foo with a couple of properties, and I want to serialize an IEnumerable of said class, again, the intent doesn’t require the extra use of attributes and a complexity overhead.
This is not to say that the DataContractJsonSerializer does not have its place; if you are leveraging WCF and choosing JSON as your serialization format, it is probably the best route to go. That said, however, I have fallen more than once into a “pit of success” with Json.NET after getting burdened with trying to use the DataContractJsonSerializer.
Json.NET is still quite active, the last release during the latter half of this year. Check it out.