For Conceptual Mass and Curtain Panel families, lock or unlock a dimension-driving parameter. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
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Exceptions
| Exception | Condition | 
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| Autodesk.Revit.Exceptions InvalidOperationException | Thrown if this family is not a Conceptual Mass or Curtain Panel family. | 
| Autodesk.Revit.Exceptions ArgumentException | Thrown if the parameter is not lockable. |