Defines metadata for an object in the type library.
The custom C++ attribute will cause information to be placed into the type library. You will need a tool that reads the custom value from type library.
The custom attribute has the same functionality as the custom MIDL attribute.
Non-COM interface, class, enums, idl_module methods, interface members, interface parameters, typedefs, unions, structs
coclass (when used on class)
For more information about the attribute contexts, see Attribute Contexts.