public Settingplacesymbolongaravity GetSetting()
        {
            Settingplacesymbolongaravity setting = SettingExtension.GetSetting <Settingplacesymbolongaravity>(GetFullFileName());

            if (setting == null)
            {
                setting = new Settingplacesymbolongaravity();
            }
            return(setting);
        }
        public Result Execute(
            ExternalCommandData commandData,
            ref string message,
            ElementSet elements)
        {
            UIApplication uiapp = commandData.Application;
            UIDocument    uidoc = uiapp.ActiveUIDocument;
            Application   app   = uiapp.Application;
            Document      doc   = uidoc.Document;
            Selection     sel   = uidoc.Selection;

            listsymbol = ListSymbol(doc);
            Setting    = Settingplacesymbolongaravity.Instance.GetSetting();
            center     = Doing(doc);
            Reference rf = sel.PickObject(ObjectType.Face);

            curves = GetCurveLoops(doc, rf);
            var form = new FrmPlaceSymbolGravity(this, doc);

            form.ShowDialog();

            return(Result.Succeeded);
        }