IUnknown
（重定向自Query Interface）
In computer programming, the IUnknown (custom) interface is the fundamental interface in the Component Object Model (COM). The published COM specification mandates that COM objects must minimally implement this interface. Furthermore, every other COM interface must be derived from IUnknown. IUnknown exposes two essential features of all COM objects: object lifetime management through reference counting, and access to various predefined interfaces.