CurveReverse Method

using Rhino;
using Rhino.Commands;
using Rhino.Input;
using Rhino.DocObjects;

namespace examples_cs
{
  public class ReverseCurveCommand : Command
  {
    public override string EnglishName { get { return "csReverseCurve"; } }

    protected override Result RunCommand(RhinoDoc doc, RunMode mode)
    {
      ObjRef[] obj_refs; 
      var rc = RhinoGet.GetMultipleObjects("Select curves to reverse", true, ObjectType.Curve, out obj_refs);
      if (rc != Result.Success)
        return rc;

      foreach (var obj_ref in obj_refs)
      {
        var curve_copy = obj_ref.Curve().DuplicateCurve();
        if (curve_copy != null)
        {
          curve_copy.Reverse();
          doc.Objects.Replace(obj_ref, curve_copy);
        }
      }
      return Result.Success;
    }
  }
}

Imports Rhino
Imports Rhino.Commands
Imports Rhino.Input
Imports Rhino.DocObjects

Namespace examples_vb
  Public Class ReverseCurveCommand
    Inherits Command
    Public Overrides ReadOnly Property EnglishName() As String
      Get
        Return "vbReverseCurve"
      End Get
    End Property

    Protected Overrides Function RunCommand(doc As RhinoDoc, mode As RunMode) As Result
      Dim objRefs As ObjRef() = Nothing
      Dim rc = RhinoGet.GetMultipleObjects("Select curves to reverse", True, ObjectType.Curve, objRefs)
      If rc <> Result.Success Then
        Return rc
      End If

      For Each objRef As ObjRef In objRefs
        Dim curveCopy = objRef.Curve().DuplicateCurve()
        If curveCopy IsNot Nothing Then
          curveCopy.Reverse()
          doc.Objects.Replace(objRef, curveCopy)
        End If
      Next
      Return Result.Success
    End Function
  End Class
End Namespace

import rhinoscriptsyntax as rs
from scriptcontext import *
import Rhino

def ReverseCurves():
    crvs = rs.GetObjects("Select curves to reverse", rs.filter.curve)
    if not crvs: return

    for crvid in crvs:
        crv = rs.coercecurve(crvid)
        if not crv: continue
        dup = crv.DuplicateCurve()
        if dup:
            dup.Reverse()
        doc.Objects.Replace(crvid, dup)

if __name__ == "__main__":
    ReverseCurves()