ULONG AddRef();
Increases the reference count of the Direct3DViewport object by 1. This method is part of the IUnknown interface inherited by Direct3DViewport.
·Returns the new reference count of the object.
When the Direct3DViewport object is created, its reference count is set to 1. Every time an application obtains an interface to the object or calls the AddRef method, the object's reference count is increased by 1. Use the IDirect3DViewport::Release method to decrease the reference count of the object by 1.