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<h1>Callbacks</h1><p>External
Callbacks enable you to add Listeners to an ObjectContainer for the following
db4o events</p>
<ul><li>QueryStarted </li><li>QueryFinished </li><li>Creating (first time an object is about to be saved) </li><li>Created (after the object is saved)</li><li>Activating </li><li>Activated </li><li>Deactivating </li><li>Deactivated</li><li>Updating </li><li>Updated</li><li>Deleting </li><li>Deleted</li><li>Committing</li><li>Committed<br></li></ul>
<p>QueryStarted
and QueryFinished events accept QueryEventArgs as a parameter and can be used
to gather query statistics information.</p>
<p>Created,
Activated, Deactivated, Updated and Deleted events accept ObjectEventArgs and
can be used to gather statistics information or to initiate some special
behavior after the action has been taken.</p>
<p>Creating,
Activating, Deactivating, Updating and Deleting events accept
CancellableObjectEventArgs. Their primary usage is to perform action validity check
and to stop the execution if necessary.</p><p>Committing event can be used to check some application-specific conditions before commit. For example it can</p><p> be used to check unique constraints. Committing event accepts CommitEventArgs as a parameter.</p><p>Committed event is raised when the container has completely finished the commit operation. Event subscribers get the notification in a separate thread. Committed event accepts CommitEventArgs. </p>
<p><div class="childTopicList">More Reading:<ul>
<li><p><a href="callbacks/event_registry_api.html" class="wikiLink">Event Registry API</a></p></li>
<li><p><a href="callbacks/possible_usecases.html" class="wikiLink">Possible Usecases</a></p></li>
<li><p><a href="callbacks/benefits.html" class="wikiLink">Benefits</a></p></li>
<li><p><a href="callbacks/commit-time_callbacks.html" class="wikiLink">Commit-Time Callbacks</a></p></li>
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This revision (4) was last Modified 2007-04-28T09:33:35 by Tetyana.
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