This demo shows how you can filter the data source of a DevExpress ASP.NET Combo Box (ASPxComboBox) editor that contains a large amount of records (approximately 20,000). For this purpose, both the ItemsRequestedByFilterCondition and ItemRequestedByValue events of the editor are handled.
In this demo, the ASPxComboBox does not perform filter operations on the entire database by itself. Instead, all required data processing is delegated to the database server, which returns only small portions of the data to be displayed by the editor.
This technique minimizes the application server's workload, and significantly reduces the application's response time. This technique, together with the 'Contains' filter mode of the ASPxComboBox editor, allows your customers to search against a large amount of data.
When the ASPxComboBox is in incremental filtering mode, it has the capability to start filtering only after an end-user has typed a specific number of symbols in the editor's text box. The FilterMinLength property can be used to define the minimum length of the filter string input. Once the minimum length is met, filtering operations are initiated.
This behavior is extremely useful when the ASPxComboBox works with a large amount of data. In this case, due to the large size of the data set, performing filtration on each symbol typed is inefficient, and may affect application performance. Thus, by delaying the start of filter operations using this minimum length requirement, you can provide end-users with more accurate results, and improve the performance of your page.