public static Rhino.Commands.Result LineBetweenCurves(Rhino.RhinoDoc doc) { Rhino.Input.Custom.GetObject go = new Rhino.Input.Custom.GetObject(); go.SetCommandPrompt("Select two curves"); go.GeometryFilter = Rhino.DocObjects.ObjectType.Curve; go.GetMultiple(2, 2); if (go.CommandResult() != Rhino.Commands.Result.Success) { return(go.CommandResult()); } Rhino.DocObjects.ObjRef objRef0 = go.Object(0); Rhino.DocObjects.ObjRef objRef1 = go.Object(1); double t0 = Rhino.RhinoMath.UnsetValue; double t1 = Rhino.RhinoMath.UnsetValue; Rhino.Geometry.Curve curve0 = objRef0.CurveParameter(out t0); Rhino.Geometry.Curve curve1 = objRef1.CurveParameter(out t1); if (null == curve0 || !Rhino.RhinoMath.IsValidDouble(t0) || null == curve1 || !Rhino.RhinoMath.IsValidDouble(t1)) { return(Rhino.Commands.Result.Failure); } Rhino.Geometry.Line line = Rhino.Geometry.Line.Unset; bool rc = Rhino.Geometry.Line.TryCreateBetweenCurves(curve0, curve1, ref t0, ref t1, false, false, out line); if (rc) { if (Guid.Empty != doc.Objects.AddLine(line)) { doc.Views.Redraw(); return(Rhino.Commands.Result.Success); } } return(Rhino.Commands.Result.Failure); }