IPersistFile::IsDirty (Windows CE 5.0)

项目
09/14/2012

This method checks an object for changes since it was last saved to its current file.

HRESULT IsDirty(void);

Parameters

None.

Return Values

S_OK
The object has changed since it was last saved.
S_FALSE
The object has not changed since the last save.

Remarks

This method checks whether an object has changed since it was last saved. Call it to determine whether an object should be saved before closing it. The dirty flag for an object is conditionally cleared in the IPersistFile::Save method.

To determine whether the platform supports this interface, see Determining Supported COM APIs.

Notes to Callers

OLE does not call IPersistFile::IsDirty. Applications would not call it unless they are also saving an object to a file.

You should treat any error return codes as an indication that the object has changed. Unless this method explicitly returns S_FALSE, assume that the object must be saved.

Notes to Implementers

An object with no contained objects simply checks its dirty flag to return the appropriate result.

A container with one or more contained objects must maintain an internal dirty flag that is set when any of its contained objects has changed since it was last saved.

To do this, the container should maintain an advise sink by implementing the IAdviseSink interface.

Then, the container can register each link or embedding for data change notifications with a call to IDataObject::DAdvise.

Then, the container can set its internal dirty flag when it receives an IAdviseSink::OnDataChange notification.

If the container does not register for data change notifications, the IPersistFile::IsDirty implementation would call IPersistStorage::IsDirty for each of its contained objects to determine whether they have changed.

The container can clear its dirty flag whenever it is saved, as long as the file to which the object is saved is the current working file after the save. Therefore, the dirty flag would be cleared after a successful Save or Save As operation, but not after a Save A Copy As operation.

Requirements

OS Versions: Windows CE 3.0 and later.
Header: Objidl.h, Objidl.idl.
Link Library: Ole32.lib, Uuid.lib.

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