IPersistStorage::IsDirty

Indicates whether the object has changed since it was last saved to its current storage.

HRESULT IsDirty(void);

Return Values

S_OK

The object has changed since it was last saved.

S_FALSE

The object has not changed since the last save.

Comments

This method checks whether an object has changed since it was last saved so you can avoid losing information in the object that has not yet been saved. The dirty flag for an object is conditionally cleared in the IPersistFile::Save method.

For example, you could optimize a File:Save operation by calling the IPersistStorage::IsDirty method for each component object and then calling the IPersistStorage::Save method only for those component objects that are dirty.

Notes to Callers

You should treat any error return codes as an indication that the object has changed. In other words, unless this method explicitly returns S_FALSE, you must assume that the object needs to be saved.

Notes to Implementors

A container object with one or more contained objects must maintain an internal dirty flag that reflects any one contained object being dirty. To do this, the container object should register for data change notifications with each link or embedding (see IDataObject::DAdvise). Then, the container can maintain its internal dirty flag that it sets when it receives an IAdviseSink::OnDataChange notification. If the container does not register for data change notifications, the IPersistFile::IsDirty implementation must call IPersistStorage::IsDirty for each of its contained objects to determine whether they have changed.

A component object can clear its dirty flag whenever it is saved, as long as the storage saved to is the current working storage after the save. In other words, the dirty flag is cleared after a successful "Save" or "Save As" operation, but not after a "Save A Copy As . . ." operation.

See Also

IAdviseSink::OnDataChange, IDataObject::DAdvise, IPersistStorage::Save

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