The AddInterface method adds an existing interface to the collection of interfaces that are implemented by a particular class.
HRESULT AddInterface(
IInterfaceDef *plInterfaceDef,
BSTR Flags
);
Parameters
Return Value
S_OK
The method completed successfully.
This method failed to complete successfully.
Remarks
When you indicate that an interface is the default interface for a class, you are actually setting the value of the ImplementsOptions annotational property on the Class_Implements_Interface relationship to TRUE. (Remember that every relationship can have annotational properties set on it.)