SPBuiltInContentTypeId class
A class that retrieves SPContentTypeId objects that represent identifiers (IDs) for built-in content types.
Namespace: Microsoft.SharePoint
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
The following example is a console application that examines where the built-in “Item” content type is used in a site collection. The application begins by building a generic list of SPContentTypeUsage objects that contain information about each use of a content type in a site collection. Then it counts the number of times that the content type is used as a site content type and the number of times it is used as a list content type. The results are printed to the console.
When the application is run against a Web site created with the Team Site template, it prints the following output to the console.
The content type is inherited by 33 site content types and 20 list content types. Press ENTER to continue...