gistfile1.cs

            try {
                if (null == commandData) {
                    throw new ArgumentNullException("commandData");
                }

                UIApplication app = commandData.Application;
                UIDocument uiDoc = app.ActiveUIDocument;
                Document doc = uiDoc.Document;

                using (Transaction transaction = new Transaction(doc)) {

                    transaction.Start("Building panels");

                    ISelectionFilter wallFilter = new WallSelectionFilter();
                    Reference wallReference = uiDoc.Selection.PickObject(ObjectType.Element,
                                                                         wallFilter,
                                                                         "Select a wall to split into panels");

                    if (wallReference != null && wallReference.ElementId != ElementId.InvalidElementId) {
                        Wall wall = doc.GetElement(wallReference.ElementId) as Wall;

                        if (wall == null) {
                            return Result.Failed;
                        }

                        IList<ElementId> wallList = new List<ElementId>();
                        wallList.Add(wallReference.ElementId);

                        LocationCurve lc = wall.Location as LocationCurve;

                        Line line = lc.Curve as Line;

                        if (null == line) {
                            message = "Unable to retrieve wall location line.";
                            return Result.Failed;
                        }

                        XYZ origin = new XYZ(line.Origin.X, line.Origin.Y, line.Origin.Z);

                        int divisions = 5;
                        IList<XYZ> divisionPoints = new List<XYZ>();
                        IList<XYZ> intersectionLineOriginPoints = new List<XYZ>();
                        IList<XYZ> intersectionLineEndPoints = new List<XYZ>();

                        for (var i = 1; i < divisions; i++) {
                            XYZ newPoint = new XYZ();
                            newPoint = origin.Add(line.Direction.Multiply(line.Length * i / divisions));
                            divisionPoints.Add(newPoint);
                        }

                        // Creating a vector colinear with the wall with length equal 2* the wall witdh
                        XYZ wallWidthVector = line.Direction.Multiply(2 * wall.Width);

                        IList<ElementId> intersectionElementIds = new List<ElementId>();
                        IList<Curve> curveArray = new List<Curve>();

                        for (var i = 0; i < divisions - 1; i++) {
                            // Creating a line for each division point
                            // Startpoint at (division point - wall width vector)
                            // Endpoint at (division point + wall width vector) 
                            Line intersectionLine = Line.CreateBound(divisionPoints[i].Add(wallWidthVector.Negate()),
                                                                     divisionPoints[i].Add(wallWidthVector));

                            // Creating a 90deg rotation transform
                            Transform rotate90Deg = Transform.CreateRotationAtPoint(XYZ.BasisZ,
                                                                                    Units.ToRadians(90),
                                                                                    divisionPoints[i]);

                            // Based on intersectionLines creating a 90deg rotated curve
                            // This curve, perpendicular to the wall will be used to define 2 things:
                            // the curve dividing the object
                            Curve intersectionCurve = intersectionLine.CreateTransformed(rotate90Deg);
                            // the reference plane dividing the object
                            ReferencePlane intersectionPlane = doc.Create.NewReferencePlane2(intersectionCurve.GetEndPoint(0),
                                                                                             intersectionCurve.GetEndPoint(1),
                                                                                             line.Direction,
                                                                                             doc.ActiveView);
                            
                            curveArray.Add(intersectionCurve);
                            intersectionElementIds.Add(intersectionPlane.Id);
                        }

                        SketchPlane divisionSketchPlane = SketchPlane.Create(doc, new Plane(new XYZ(0, 0, 1), line.Origin));

                        if (PartUtils.AreElementsValidForCreateParts(doc, wallList)) {
                            PartUtils.CreateParts(doc, wallList);
                            doc.Regenerate();

                            ICollection<ElementId> parts = PartUtils.GetAssociatedParts(doc, wall.Id, false, false);

                            if (PartUtils.ArePartsValidForDivide(doc, parts)) {
                                PartUtils.DivideParts(doc, parts, intersectionElementIds, curveArray, divisionSketchPlane.Id);
                            }

                            doc.ActiveView.PartsVisibility = PartsVisibility.ShowPartsOnly;
                        }
                    }

                    transaction.Commit();
                }
                return Result.Succeeded;

            } catch (Exception e) {
                message = e.Message;
                return Result.Failed;
            }