In .NET world, when it comes to object serialization, it usually goes into inspecting the object's fields and properties at runtime. Using reflection for this job is usually slow and is undesirable when dealing with large sets of objects. The other way is using IL emit or building expression trees that provide significant performance gain over reflection. And the latter is most modern libraries pick when dealing with serialization. However building and emitting IL at runtime takes time, and the investment is only paid back if this information is cached and reused for objects of the same type.

When using Json.NET, it is not clear to me which method described above is used, and if the latter is indeed used, whether the caching is used.

For example, when I do:

JsonConvert.SerializeObject(new Foo { value = 1 });

Does Json.NET build the Foo's member access info and cache to reuse it later?