ASPxTreeList.BeforeHeaderFilterFillItems Event
Enables you to provide custom filter items instead of default ones displayed within a Header Filter.
Namespace: DevExpress.Web.ASPxTreeList
Assembly: DevExpress.Web.ASPxTreeList.v19.2.dll
Declaration
public event ASPxTreeListBeforeHeaderFilterFillItemsEventHandler BeforeHeaderFilterFillItemsEvent Data
The BeforeHeaderFilterFillItems event's data class is ASPxTreeListBeforeHeaderFilterFillItemsEventArgs. The following properties provide information specific to this event:
| Property | Description |
|---|---|
| Column | Gets the data column currently being filtered. |
| Handled | Specifies whether the BeforeHeaderFilterFillItems event is handled. Inherited from ASPxGridBeforeHeaderFilterFillItemsEventArgs. |
| Values | Gets a collection that contains the header filer values. Inherited from ASPxGridHeaderFilterEventArgs. |
The event data class exposes the following methods:
| Method | Description |
|---|---|
| AddShowAll() | Adds the ‘All’ item to the header filter. Inherited from ASPxGridHeaderFilterEventArgs. |
| AddShowBlanks(String) | Creates and adds the “Blanks” filter value to the header filter values. Inherited from ASPxGridHeaderFilterEventArgs. |
| AddShowNonBlanks(String) | Creates and adds the “(Non blanks)” filter value to the header filter values. Inherited from ASPxGridHeaderFilterEventArgs. |
| AddValue(String, CriteriaOperator) | Adds a new filter item with the specified filter criteria operator to the header filter. Inherited from ASPxGridBeforeHeaderFilterFillItemsEventArgs. |
| AddValue(String, String, String) | Adds a new filter item with the specified filter criteria to the header filter. Inherited from ASPxGridHeaderFilterEventArgs. |
| AddValue(String, String) | Adds a new filter item to the header filter. Inherited from ASPxGridHeaderFilterEventArgs. |
| CreateShowBlanksValue(String) | Creates and returns the (Blanks) filter item used to filter a column by blank values. Inherited from ASPxGridHeaderFilterEventArgs. |
| CreateShowNonBlanksValue(String) | Creates and returns the (Non blanks) filter item used to filter a column by blank values. Inherited from ASPxGridHeaderFilterEventArgs. |
Remarks
End-users can filter column values using the Header Filter. To invoke the header filter, an end-user should click on the filter button. The BeforeHeaderFilterFillItems event is raised before the header filter is shown and default filter items are created. The event enables you to provide custom filter items.
The data column whose filter button has been clicked is returned by the ASPxTreeListBeforeHeaderFilterFillItemsEventArgs.Column property. To add a new filter value, use the ASPxGridBeforeHeaderFilterFillItemsEventArgs.AddValue method.
Set the ASPxGridBeforeHeaderFilterFillItemsEventArgs.Handled property to true to prevent the ASPxTreeList.HeaderFilterFillItems event from being raised. Otherwise, the event clears the item collection before filling it with default items.
If you would like to add custom items to the default items, use the ASPxTreeList.HeaderFilterFillItems event.
The ASPxTreeList header filter allows the use of HTML tags in an item text. To learn more, see Header Filter .
Note
Online Demos Refer to the Tree List - Header Filter (Web Forms) online demo to review how to filter Tree List data nodes using the Header Filter.