An element that establishes the placement of a view on a sheet. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2013 
Syntax
Remarks
 Viewports are used in Revit for purposes other than placement of views on sheets. Thus iteration of viewport elements in the model may locate viewports which are not assigned to sheets; you can use the SheetId property to filter these out.