GridView - How to implement the Select All feature for a CheckBox column in Batch Edit mode

In this example, GridView is used in Batch Edit mode. The IsRequired column's HeaderTemplate is replaced with CheckBox. Clicking the header's check box causes setting all cells of the IsRequired column to true by using the ASPxClientGridViewBatchEditApi method.
See also: ASPxGridView - How to implement the Select All feature for GridViewDataCheckBoxColumn when the Batch Edit mode is used.