The identifier of the project (on the Green Building Studio server) that was selected by the user. 
   Namespace:   Autodesk.Revit.UI  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 16.0.0.0 (16.0.0.0) 
  Since:  2016 
Syntax
Remarks
 This value is only valid after  Show  has been called. A negative value indicates that no project was selected.