The DockPanel extension has the capability to load panel content on demand via callbacks. Several content loading modes are available via the following settings of the LoadContentViaCallback property.
- None - The content is always (initially) rendered inside a dock panel (the default behavior).
- OnPageLoad - Loading of panel contents starts immediately after an entire page has been loaded.
- OnFirstShow - Loading of panel contents starts when a dock panel is invoked for the first time.
- OnDock - Loading of panel contents starts every time a panel has been docked to a dock zone.
- OnDockStateChange - Loading of panel contents starts every time a panel's dock state has been changed (that is a docked panel starts floating or a floated panel docks to a zone).
- OnFloating - Loading of panel contents starts every time a panel has been made floated.
Using a postponed load of panel contents, you can enhance the response time of your web page on its initial load. You can also update the content of a dock panel programmatically on demand.
Note that in this example, we purposely pause callback processing on the server side for half a second in order to make the loading panel visible during this time.