The category ID of elements appearing in the schedule.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 25.0.0.0 (25.0.0.0)
public ElementId CategoryId { get; }
Most schedules show elements of a single category. In multi-category schedules, the category ID is InvalidElementId. In key schedules, the schedule’s category is the category of elements that the keys are associated with.