Remove the parameter from the definition. 
   Namespace:   Autodesk.Revit.DB.Structure  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2009 
Syntax
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Parameters
- paramId
-  Type:  Autodesk.Revit.DB ElementId  
 Id of a parameter in the definition.
Remarks
 If the definition does not have the parameter, the method does nothing. 
 Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was NULL | 
| Autodesk.Revit.Exceptions DisabledDisciplineException | None of the following disciplines is enabled: Structural. |