The family parameter label of the dimension. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 17.0.0.0 (17.0.1090.0) 
  Since:  2014 
Syntax
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| Visual Basic | 
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Remarks
 A dimension only can be labeled to a family parameter in a family document. When the dimension is labeled by a reporting parameter, the dimension value drives the parameter value. When the parameter is labeled by a non-reporting, the value of the parameter drives the dimension. If the dimension is multi-segmented, each segment of the dimension is driven by the same parameter value. Multi-segmented dimensions cannot be labeled by reporting parameters. To unbind the family parameter, set this property to    a null reference (  Nothing  in Visual Basic)  . 
 Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentException | Thrown when the family parameter's ParameterType is not suitable for this dimension. | 
| Autodesk.Revit.Exceptions InvalidOperationException | Thrown when dimension can not be labeled. | 
| Autodesk.Revit.Exceptions InvalidOperationException | Thrown when failed to get the BuiltInParameter DIM_LABEL. |