Create new Form element by cap operation (to create a single-surface form), and add it into the Autodesk Revit family document. 
   Namespace:   Autodesk.Revit.Creation  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
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Parameters
- isSolid
 -  Type:  System Boolean  
Indicates if the Form is Solid or Void. 
- profile
 -  Type:  Autodesk.Revit.DB ReferenceArray  
The profile of the newly created cap. It should consist of only one curve loop.