The error level that the routing preference manager should post errors if the routing conditions do not meet any routing preference rule, could be None, Warning, or Error 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2013 
Syntax
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Exceptions
| Exception | Condition | 
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| Autodesk.Revit.Exceptions ArgumentOutOfRangeException | When setting this property: A value passed for an enumeration argument is not a member of that enumeration | 
| Autodesk.Revit.Exceptions DisabledDisciplineException | When setting this property: None of the following disciplines is enabled: Mechanical Electrical Piping. |