Hi Peter,
Thank you for your update.
You can achieve your requirement by setting PersistGroupsExpandState as True like shown below,
Code Snippet[XAML]
For your reference, please find the sample in the below location,
Sample:
<
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=SyncWPFDataGrid-684545635.zip >
Please let us know if you have any queries.
Thanks,
Rajasekar