Create a fixed segment direction constraint. 
   Namespace:   Autodesk.Revit.DB.Structure  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2012 
Syntax
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Parameters
- dir
-  Type:  Autodesk.Revit.DB UV  
 A fixed direction in UV-space.
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was NULL | 
| Autodesk.Revit.Exceptions ArgumentOutOfRangeException | dir has zero length. |