The view that is currently active. 
   Namespace:   Autodesk.Revit.UI.Events  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2010 
Syntax
Remarks
 May be    a null reference (  Nothing  in Visual Basic)  if there is no currently active view.