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Dynamic List Population (Filtering Large Data Sources)

The ASPxComboBox provides you with the ability to manually populate a dropdown list with the required item portions, based on the currently applied filter criteria and the performed list scrolling. For instance, when using a large data source, you can only request a few records to be visible on screen. The rest of the items can be loaded on demand, while an end-user is scrolling the list.

In this mode, all data-aware operations (such as filtering) are intended to be performed on the database server side. This means that you can significantly decrease web server workload by loading only a subset of all items when working with large datasets. All of this guarantees rapid data processing and display.

To manually supply list data to the ASPxComboBox editor, you should enable the callback mode (by setting the ASPxAutoCompleteBoxBase.EnableCallbackMode property to True) and handle the following two events: ASPxComboBox.ItemsRequestedByFilterCondition and ASPxComboBox.ItemRequestedByValue.

Handling these events, together with using the 'Contains' filter mode of the ASPxComboBox editor, allows you to deliver your customers the capability for fast and efficient searches against a large amount of data.

Expanded Online Demo

Expanded Example

The following section of the Filtering Large Data Source online demo illustrates how the ASPxComboBox.ItemsRequestedByFilterCondition and ASPxComboBox.ItemRequestedByValue events of the ASPxComboBox editor can be handled to filter the editor's data source containing a large number of records.

Note

To work properly, both the ItemsRequestedByFilterCondition and ItemRequestedByValue events should be handled.

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