Use SelectByID2 on the selection to remove it from selection list, pass the Append parameter of this method as True,
Take a look at the following link for details,
If... And if entity is... Then... True Not already selected The entity is appended to the current selection list Already selected The entity is removed from the current selection list false Not already selected The current selection list is cleared, and then the entity is put on the list Already selected The current selection list remains the same
Use SelectionMgr::DeSelect2 where the 'AtIndex' parameters equals to all selection indices from your selection box (from PropertyManagerPageSelectionbox::SelectionIndex to PropertyManagerPageSelectionbox::SelectionIndex[IPropertyManagerPageSelectionbox::ItemCount]) and 'mark' parameter equals to your selection mark parameter (PropertyManagerPageSelectionbox::Mark)
Regards, Artem Taturevych | Snr. Developer | IC3D ANZ
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Thanks Santosh Pawar and Artem Taturevych for your help!
It's my mistake, IModelDoc2::ClearSelection2 can be clear current selections.