Identify a Preinstalled Content Type

Question

Does anyone know of a fast way to tell through code if a ContentType is one that's a pre-installed one?

Conversely, I want to know if a given ContentType was provisioned by a custom feature / generated by the user through the WebUI.

Sure, there are short ContentTypeIds (like 0x0102) and long ones (0x0100<flattened guid>), but is there any other way?

I'm asking for any version, 2007 or 2010.

Answer 1

http://www.pvle.be/2011/01/is-a-given-field-one-of-sharepoints-built-in-field/

Answer 2

Try this:

SPContentType ct;
//set your content type
bool builtIn = SPBuiltInContentTypeId.Contains(ct.Id);