Return the parameter's formula, if one is associated with it. 
   Namespace:   Autodesk.Revit.DB.Structure  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2009 
Syntax
| C# | 
|---|
   |  
| Visual Basic | 
|---|
   |  
| Visual C++ | 
|---|
   |  
Parameters
- paramId
 -  Type:  Autodesk.Revit.DB ElementId  
Id of a parameter in the definition. 
Return Value
The formula, or an empty string if there is no formula for the parameter.Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | This RebarShapeDefinition does not have a value for the parameter paramId. | 
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was NULL |