One way to change the desired images is to edit the theme(s) that you use and set the images to the appropriate states for the ExpanderItem (see attached image). You can use Visual Style Builder
to edit your themes.
Alternatively, you cause the ViewCellFormatting event to do that:
sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
GridGroupExpanderCellElement expanderCell = e.CellElement
expanderCell.Expander.SignImage = Resources.expanded;
expanderCell.Expander.SignImage = Resources.collapsed;
In addition you might need to invalidate the row when an expand action occurs. The GroupExpanded event is suitable for this:
sender, GroupExpandedEventArgs e)
I hope that you find this information useful. Should you have any other questions, do not hesitate to contact us.
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