Hi Rayzhahng,
Thanks for your interest in Syncfusion products.
From your query, I understand that you need to set check box in the group header for that please refer the following code snippet.
<code>
if (e.TableCellIdentity.DisplayElement.Kind==Syncfusion.Grouping.DisplayElementKind.GroupHeader && e.TableCellIdentity.Column != null )
{
e.Style.CellType = GridCellTypeName.CheckBox;
}
</code>
After that check if the check box is selected using "QueryCellInfo" event. If it is selected add the the records in "Selected Record.AddRanges()".
Please let me know if this helps you.
Regards,
Jeya Preetha M