This sample demonstrates the use of the AJAX-based callbacks implemented by the ASPxNavBar control.
The ASPxNavBar control supports AJAX technology by implementing the ability to load the content of a group from the server via a callback when the group is expanded. This approach allows the navbar to avoid the initial transfer of all its group's data to the client, thus optimizing the page's load time.
In order to enable the use of callbacks, its EnableCallBacks property should be set to true. In this instance, the contents of the collapsed groups are not represented on the client. When a group is expanded for the first time, its content is retrieved from the server and then cached on the client. The next time the group is expanded, its content is taken from the client and no callback to the server is performed.
In addition, this example uses the ASPxPopupMenu to enable all the groups to be expanded or collapsed on the client side (without PostBack). To do this, you can right-click the navbar and select either the 'Expand All' or 'Collapse All' option.
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.