IDataObject  LQWB47

The IDataObject interface specifies methods that enable data transfer and notification of changes in data. Data transfer methods specify the format of the transferred data along with the medium through which the data is to be transferred. Optionally, the data can be rendered for a specific target device. In addition to methods for retrieving and storing data, the IDataObject interface specifies methods for enumerating available formats and managing connections to advisory sinks for handling change notifications.

The term  data object  is used to mean any object that supports an implementation of the IDataObject interface. Implementations vary, depending on what the data object is required to do; in some data objects, the implementation of certain methods not supported by the object could simply be the return of E_NOTIMPL. For example, some data objects do not allow callers to send them data. Other data objects do not support advisory connections and change notifications. However, for those data objects that do support change notifications, OLE provides an object called a data advise holder. An interface pointer to this holder is available through a call to the helper function CreateDataAdviseHolderAP85R9. A data object can have multiple connections, each with its own set of attributes. The OLE data advise holder simplifies the task of managing these connections and sending the appropriate notifications.

When to Implement

Implement the IDataObject interface if you are developing a container or server application that is capable of transferring data. For example, if your application allows its data to be pasted or dropped into another application, you must implement the IDataObject interface. OLE compound document object servers that support objects that can be embedded or linked must implement IDataObject.

OLE provides implementations in its default object handler and its cache.

When to Use

Any object that can receive data calls the methods in the IDataObject interface.

When you call the data transfer methods in the IDataObject interface, you specify a format, a medium, and, optionally, a target device for which the data should be rendered. Objects, such as containers, that want to be notified through their advise sinks when the data in the data object changes call the IDataObject advisory methods to set up an advisory connection through which notifications can be sent.

Methods in VTable Order