Gets the hash code of this document instance. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
Remarks
 The hash code is the same for document instances that represent the same document currently opened in the Revit session. The hash code is generated when a Revit file is opened or created in session. If the same Revit file is opened later (in the same session or a different session) the hash code will not be the same.