The id of the category or sub category in which the elements that this family could generate reside. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2015 
Syntax
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | When setting this property: The input category id cannot be assigned as the new category for this family. | 
| Autodesk.Revit.Exceptions ArgumentNullException | When setting this property: A non-optional argument was NULL | 
| Autodesk.Revit.Exceptions InvalidOperationException | When setting this property: The family is not an owner family for its own editable document. |