获取Marshal.GetIDispatchForObject后如何调用GetTypeInfoCount？

Question

我在Managed Environment（C＃）中获取了指向IDispatch的IntPtr指针，如何调用此接口的方法，如GetTypeInfoCount，GetTypeInfo和GetIDsOfNames？

IntPtr pointer = Marshal.GetIDispatchForObject(_browser.Document);
// Marshal.XXXX(pointer).GetTypeInfoCount() ?