Centerpoint reference of curve element. Curves such as circles, arcs, ellipses, and partial ellipses support this property. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
Remarks
 Use this reference property when using the API to dimension between centerpoints of curves.