Grouped elements can only be deleted when the group is being edited. To delete a member select the group and then click the Edit Group button on the toolbar, then delete the member.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.2.0.0 (26.2.0.0)
Syntax
C#
public static FailureDefinitionId DeletePreventedByGroup { get; }