C1WebTopicBar's groups can be populated on demand statically, dynamically, or in a data-driven tree view. The phrase PopulateOnDemand implies that only the information from the selected group an end-user clicks on is sent to the server. This increases the usability and functionality of the C1WebTopicBar by enabling it to handle large amounts of data without affecting C1WebTopicBar's performance. The PopulateOnDemand feature supports the AJAX mechanism which causes the information in the group to load on demand through callbacks rather than postbacks.
Populate On Demand in Static and Data-Driven Tabs
To enable this feature, in a data-driven or static C1WebTopicBar, set the C1WebTopicBarGroup's PopulateOnDemand property to True at design time.
Populate On Demand in Dynamic Tab Groups
Like static and data-driven tab strips, dynamic topic bars can also use the PopulateOnDemand feature to enable callbacks. The groups can be populated dynamically through the GroupPopulate event.
How the PopulateOnDemand Property Functions
AJAX allows C1WebTopicBar to load data without having to do a postback to the server, minimizing load time and greatly improving the end-user experience. Using C1WebTopicBarGroup's PopulateOnDemand feature, the information in the selected group calls back to the server to retrieve only the information that is requested, unlike with a server postback, where the whole page must be reloaded to update the C1WebTopicBar. End-users can quickly view each group in the C1WebTopicBar without seeing the flicker on the screen during load time.
Visual Cues During CallBacks
You can also use a visual cue to show the callback is working when the user clicks something that triggers AJAX actions. For example, C1WebTopicBar has two properties, CallbackWaitImageUrl and CallbackWaitControlID that can be set to provide visual feedback and enhance the application.
The CallbackWaitImageUrl
property shows a default spinner 
when the AJAX action is triggered. This improves the
usability of the Web application by allowing the user to see the AJAX action
performing. You can specify a different image by changing the setting in the CallbackWaitImageUrl
property. The CallbackWaitControlID
property functions the same way, except that it shows a control rather than an
image.
Note: If both the CallbackWaitControlID and CallbackWaitImageURL properties are set, CallbackWaitControlID takes precedence over the CallbackWaitImageURL, and only the control appears.
For information on how to use the CallbackWaitImageUrl or CallbackWaitControlID property, see Using Visual Cues During a CallBack.
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