/// <summary>
        /// Adds given MainWindow to structure manager MainWindow list.
        /// </summary>
        public static void Add_MainWindow(IMainWindow mainWindow)
        {
            if (MainWindow_Root == null)
            {
                MainWindow_Root = mainWindow;
            }

            MainWindows_List.Add(new MainWindow_Children_List(mainWindow));
        }
        /// <summary>
        /// Removes given MainWindow out off structer manager.
        /// </summary>
        static internal List <IMainWindow_Children> Remove_MainWindow(IMainWindow mainWindow)
        {
            MainWindow_Children_List MainWindow_Children_List = Get_MainWindow_Children_List(mainWindow);

            List <IMainWindow_Children> Children_List = MainWindow_Children_List.This_Children_List;

            MainWindows_List.Remove(MainWindow_Children_List);

            return(Children_List);
        }