Data Virtualization is a useful technique for handling large amounts of data in connected scenarios. RadDataBoundListBox supports three modes of data
virtualization which can be used by setting the DataVirtualizationMode property. Each virtualization mode brings different user experience and is suitable for certain
types of scenarios. The three virtualization modes are as follows:
The Automaticis used together with an instance of the VirtualizingDataCollection class as ItemsSource for the control. In this mode only
those data items are fetched which are currently to be displayed in the control. When an item is not loaded, a specialized ItemLoadingTemplate is displayed instead of the
ItemTemplate defined on the RadDataBoundListBox control.
The OnDemandManual mode is a mode in which data is fetched upon a request from the end-user. The request is usually made by tapping on a specialized item
displayed at the end of the scrollable list in the control.
The OnDemandAutomatic mode is a mode in which data is fetched automatically when the end-user reaches the end of the scrollable list. A specialized progress
bar may be displayed at the end of the scrollable list indicating that a data download operation is performed.
The None option simply indicates that the RadDataBoundListBox control will work in its default data handling mode, i.e. it will visualize the items
from its ItemsSource.
DataVirtualizationItemContent and DataVirtualizationItemTemplate
The RadDataBoundListBox control exposes the DataVirtualizationItemContentand DataVirtualizationItemTemplate properties which are used in
context with the OnDemandManual virtualization mode. These properties enable the developer to customize the contents and appearance of the specialized
visual item displayed at the end of the scrollable list that can be used to manually request more data to be loaded.
ItemLoadingContent and ItemLoadingTemplate
The RadDataBoundListBox control exposes the ItemLoadingContentand ItemLoadingTemplate properties which are used in context with the
OnDemandAutomatic and Automatic data virtualization modes. These properties enable the developer to customize the contents and appearance of
the visual item displayed to indicate that a data request is being processed (in the case of the OnDemandAutomatic data virtualization mode) or the data for
the current visual container in the list box is not currently available (in the case of the Automatic virtualization mode).