External   |  
 The full class name for the class providing the entry point to decide availability of this menu item. 
 Namespace: Autodesk.Revit.UI
Assembly: RevitAPIUI (in RevitAPIUI.dll) Version: 25.0.0.0 (25.0.0.0)
| Exception | Condition | 
|---|---|
| ArgumentNullException | When setting this property: A non-optional argument was null | 
 This is the class implementing IExternalCommandAvailability interface.