Sorry, those was a wrong suggestion.
I attached the sample that implements this behaviour. Note that it will work with the build 3.0.20082.49 or later.
The key points are:
1) The sample redefines the C1DataGrid.UniversalItemContentTemplate. The custom template is an exact copy of the original template with the CellsAutoLayoutPresenter element replaced with the custom HideGroupedCellsAutoLayoutPresenter element implemented in the sample. The template is for the default tabular view with vertical row distribution. For the other views you need to get a corresponding template from XAML sources and replace the CellsAutoLayoutPresenter element with HideGroupedCellsAutoLayoutPresenter.
2) The HideGroupedCellsAutoLayoutPresenter class is derived from CellsAutoLayoutPresenter and overrides the GetColumnCollection method so as the returning collection contains only non-grouped columns from the C1DataGrid.ActualOrdinaryColumns collection.
In the future builds we'll add a property controlling this behaviour, so retemplating will not be needed.
Thanks,
Alex
If i set Collapsed to a column it disappear from the table and from the GroupByArea and i can't see it ...
http://helpcentral.componentone.com/cs/forums/p/75174/204615.aspx#204615