To sum them up, you should specify a custom template as the GroupHeaderTemplate of your RadGridView instance and modify that to your liking. Here's an example:
<DataTemplate x:Key="GroupHeaderTemplate">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Group.Key}" />
</StackPanel>
</DataTemplate>
Bear in mind that the data context of this template is of type GroupViewModel.
I hope you find this information helpful.
Regards,
Dilyan Traykov
Telerik by Progress
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