The ASPxPopupControl has a capability to load the content of popup windows on demand. Several content loading modes are available via the following settings of the LoadContentViaCallback property:
- None - The content is always (initially) rendered inside popup windows (the default behavior).
- OnPageLoad - Loading of popup window contents starts immediately after the entire page has been loaded.
- OnFirstShow - Loading of popup window contents starts when a popup window is invoked for the first time.
Using the postponed load of popup window contents, you can enhance the response time of your web page on its initial load. You can also update the content of popup windows programmatically, on demand.
Note that in this example we purposely pause callback processing on the server side for a second in order to make the Loading Panel visible during this time.