RhinoCommon:doc.Objects.Replace

doc.Objects可以直接replace

    public static Result ExtendCurve(RhinoDoc doc)
    {
        ObjRef[] boundary_obj_refs;
        var rc = RhinoGet.GetMultipleObjects("Select boundary objects", false, ObjectType.AnyObject, out boundary_obj_refs);
        if (rc != Result.Success)
          return rc;
        if (boundary_obj_refs == null || boundary_obj_refs.Length == 0)
          return Result.Nothing;

        var gc = new GetObject();
        gc.SetCommandPrompt("Select curve to extend");
        gc.GeometryFilter = ObjectType.Curve;
        gc.GeometryAttributeFilter = GeometryAttributeFilter.OpenCurve;
        gc.DisablePreSelect ();
        gc.Get();
        if (gc.CommandResult() != Result.Success)
          return gc.CommandResult();
        var curve_obj_ref = gc.Object(0);

        var curve = curve_obj_ref.Curve();
        if (curve == null) return Result.Failure;
        double t;
        if (!curve.ClosestPoint(curve_obj_ref.SelectionPoint(), out t))
          return Result.Failure;
        var curve_end = t <= curve.Domain.Mid ? CurveEnd.Start : CurveEnd.End;

        var geometry = boundary_obj_refs.Select(obj=> obj.Geometry());
        var extended_curve = curve.Extend(curve_end, CurveExtensionStyle.Line, geometry);
        if (extended_curve != null && extended_curve.IsValid)
        {
          if (!doc.Objects.Replace(curve_obj_ref.ObjectId, extended_curve))
        return Result.Failure;
          doc.Views.Redraw();
        }
        else
        {
          RhinoApp.WriteLine("No boundary object was intersected so curve not extended");
          return Result.Nothing;
        }

        return Result.Success;
    }