RhinoCommon API
CurveGetLength Method (Double, Interval) | 
Get the length of a sub-section of the curve.
Namespace: Rhino.Geometry
Assembly: RhinoCommon (in RhinoCommon.dll)
public double GetLength( double fractionalTolerance, Interval subdomain )
Public Function GetLength ( fractionalTolerance As Double, subdomain As Interval ) As Double
Parameters
- fractionalTolerance
 - Type: SystemDouble
Desired fractional precision. fabs(("exact" length from start to t) - arc_length)/arc_length <= fractionalTolerance. - subdomain
 - Type: Rhino.GeometryInterval
The calculation is performed on the specified sub-domain of the curve (must be non-decreasing). 
Return Value
Type: DoubleThe length of the sub-curve on success, or zero on failure.