# IDataAdviseHolder

The IDataAdviseHolder interface contains methods that create and manage advisory connections between a data object and one or more advise sinks. Its methods are intended to be used to implement the advisory methods of IDataObject. IDataAdviseHolder is implemented on an advise holder object. Its methods establish and delete data advisory connections and send notification of change in data from a data object to an object that requires this notification, such as an OLE container, which must contain an advise sink.

Advise sinks are objects that require notification of change in the data the object contains and implement the IAdviseSink interface. Advise sinks are also usually associated with OLE compound document containers.

##### When to implement

Typically, you use the OLE-provided implementation of IDataAdviseHolder to simplify your implementation of the DAdvise, DUnadvise, and EnumDAdvise methods in the IDataObject interface, and to send notification of data change as appropriate. It would be necessary to implement IDataAdviseHolder only in the case where there may be a need for a custom data advise holder object, whose methods are to be used to implement the IDataObject methods in a set of servers.

##### When to use

Your implementation of the advisory methods of IDataObject can call the methods in IDataAdviseHolder. The first time you receive a call to IDataObject::DAdvise, call the function CreateDataAdviseHolder to create an instance of the OLE-provided advise holder and get a pointer to its IDataAdviseHolder interface. Then, in implementing the IDataObject interface on the data object, you delegate implementations of the DAdvise, DUnadvise, and EnumDAdvise methods to the corresponding methods in IDataAdviseHolder.

When the data of interest to an advise sink actually changes, you call IDataAdviseHolder::SendOnDataChange from the data object to carry out the necessary notifications.

Methods in VTable Order

IUnknown Methods | Description
QueryInterface | Returns pointers to supported interfaces.
AddRef | Increments reference count.
Release | Decrements reference count.

IDataAdviseHolder Methods | Description
Advise | Creates a connection between an advise sink and a data object so the advise sink can receive notification of change in the data object.
Unadvise | Destroys a notification connection previously set up with the Advise method.
EnumAdvise | Returns an object that can be used to enumerate the current advisory connections.
SendOnDataChange | Sends a change notification back to each advise sink that is currently being managed.

See Also

IDataObject, IAdviseSink