revit api選擇Element上的點畫線

 public Result Execute(ExternalCommandData data, ref string message, ElementSet elements)
 {
     try
     {
         UIApplication uiApp = data.Application;
         UIDocument uiDoc = uiApp.ActiveUIDocument;

         Reference oPickRef1 = uiDoc.Selection.PickObject(ObjectType.PointOnElement, "請選擇起點.");
         XYZ p1 = oPickRef1.GlobalPoint;
         Reference oPickRef2 = uiDoc.Selection.PickObject(ObjectType.PointOnElement, "請選擇終點.");
         XYZ p2 = oPickRef2.GlobalPoint;

         uiDoc.Document.NewLine(p1, p2);

         return Result.Succeeded;
     }
     catch (Exception ex)
     {
         TaskDialog.Show("Error", ex.Message);
         return Result.Failed;
     }
 }

說明：
GlobalPoint爲元素命中位置。
使用平面視圖時，GlobalPoint的Z值無意義。