OBSOLETE - CheckComboBox filtering in the Auto Filter Row

UPDATED #2:

Please note that starting with version v13.1, ASPxGridView provides the column's FilterTemplate that allows using ASPxGridLookup as a multi-select AutoFilterRow editor. So, if you need to accomplish this task using the AutoFilterRow filter type (i.e., not the built-in multi-select Header Filter), consider using the approach illustrated in the E4521: ASPxGridView - How to change a default editor to ASPxGridLookup in FilterRow via FilterTemplate example instead.

UPDATED #1:

Please note that starting with version v12.1, ASPxGridView supports such a feature out-of-the-box. Please refer tot he Header Filter topic for details. For older versions, you can use the following solution.

This example demonstrates how to introduce a multi-select dropdown list, based upon column values, in the Auto Filter Row editor of a column.
 

1. There are two columns using an ASPxDropDownEdit editor with a checked ASPxListBox in its dropdown template.

The DropDownEditProperties object should be instantiated in the ASPxGridView.AutoFilterCellEditorCreate event handler as usual, but its adjustment should be performed in the ASPxGridView.AutoFilterCellEditorInitialize event handler.

2. When selecting/unselecting an item in the listbox, the corresponding element is added to the GridView's a filter condition with the GroupOperatorType.Or condition.

See Also:
Date range filtering in the Filter Row
ASPxGridView - Date auto filter
How to implement a CheckComboBox editor in the ASPxGridView