ImGearARTPage Class provides a facility called "mark groups" (or just "groups", for short) that provides a powerful mechanism for implementing application features. Every mark belongs to one and only one group; by default all marks belong to a group with index 0 and named  "[Untitled]".  Your application can create as many groups as needed - each group is given a unique index. ImGearARTPage Class provides a set of methods that manipulate all of the marks in a group (hide them all, make them all visible, etc.). Your application could use groups to provide annotation layers (each "layer" would simply be a group), so that the user could choose which layer, and thus which set of annotations to view. Alternatively, your application could use groups to provide private annotations (each person would only be able to see "their" annotations).

The various methods that operate on groups are provided by ImGearARTGroup Class and ImGearARTGroupArray Class objects. 

The same group cannot be added to the same or another ART page (via ImGearARTPage.Groups property) twice; it must be cloned prior to doing it again, otherwise the ImGearException will be thrown. To control whether the group already has parent page please use ImGearARTGroup.ParentPage property. See sample code below:

ImGearARTPage artPage = new ImGearARTPage();
ImGearARTGroup group = new ImGearARTGroup("Group1", "ART Group");
artPage.Groups.Add(group);

ImGearARTPage otherPage = new ImGearARTPage();
if (group.ParentPage != null)
 {
     group = group.Clone();
 }

otherPage.Groups.Add(group);