IPart::UnregisterControlChangeCallback method (devicetopology.h)

The UnregisterControlChangeCallback method removes the registration of an IControlChangeNotify interface that the client previously registered by a call to the IPart::RegisterControlChangeCallback method.

Syntax

HRESULT UnregisterControlChangeCallback(
  [in] IControlChangeNotify *pNotify
);

Parameters

[in] pNotify

Pointer to the IControlChangeNotify interface whose registration is to be deleted. The client passed this same interface pointer to the part object in a previous call to the IPart::RegisterControlChangeCallback method. If the UnregisterControlChangeCallback method succeeds, it calls the Release method on the client's IControlChangeNotify interface.

Return value

If the method succeeds, it returns S_OK. If it fails, possible return codes include, but are not limited to, the values shown in the following table.

Remarks

Before the client releases its final reference to the IControlChangeNotify interface, it should call UnregisterControlChangeCallback to unregister the interface. Otherwise, the application leaks the resources held by the IControlChangeNotify and IPart objects. Note that the IPart::RegisterControlChangeCallback method calls the client's IControlChangeNotify::AddRef method, and UnregisterControlChangeCallback calls the IControlChangeNotify::Release method. If the client errs by releasing its reference to the IControlChangeNotify interface before calling UnregisterControlChangeCallback, the IPart object never releases its reference to the IControlChangeNotify interface. For example, a poorly designed IControlChangeNotify implementation might call UnregisterControlChangeCallback from the destructor for the IControlChangeNotify object. In this case, the client will not call UnregisterControlChangeCallback until the IPart object releases its reference to the IControlChangeNotify interface, and the IPart object will not release its reference to the IControlChangeNotify interface until the client calls UnregisterControlChangeCallback. For more information about the AddRef and Release methods, see the discussion of the IUnknown interface in the Windows SDK documentation.

Requirements

See also

IControlChangeNotify Interface

IPart Interface

IPart::RegisterControlChangeCallback