LoadingWindow _loadingWindow;

        void ShowLoadingWindow()
        {
            if (_loadingWindow == null)
                _loadingWindow = new LoadingWindow();
            _loadingWindow.Show();
        }

        void HideLoadingWindow()
        {
            if (_loadingWindow != null)
            {
                _loadingWindow.Close();
                _loadingWindow.Dispose();
            }
        }
        bool done = false;
        void LoadSomething()
        {
            while(!done)
            {
                InitializeComponent();
                done = true;
            }
            // after code is finished, close the form
            MethodInvoker closeForm = delegate { HideLoadingWindow(); };
            _loadingWindow.Invoke(closeForm);
        }

        public MainWindow()
        {
            ShowLoadingWindow();
            new Thread(LoadSomething).Start();
        }