Indicates if this dimension is locked. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
Remarks
 This property always returns false if the dimension is a radial or spot dimension. This property cannot be set if the dimension has been labeled, or if the dimension shape is arc-length, radial, diameter or spot, or if the dimension is linear with more than one segment.