C# 关闭窗口后对象状态不清晰

我有以下代码：

    private void ShowOfflineIMs(bool hasOffline)
    {
        if (hasOffline)
        {
            _offlineDisplayerThread = new Thread(OpenOfflineWindow);
            _offlineDisplayerThread.SetApartmentState(ApartmentState.STA);
            _offlineDisplayerThread.Start();
        }
    }

    private void OpenOfflineWindow()
    {
        var offlineWindow = new OfflineWindow();
        offlineWindow.Closed += (sender, args) => Dispatcher.ExitAllFrames();
        offlineWindow.Show();
        Dispatcher.Run();
    }

关闭窗体后，窗体对象将其状态保留在窗口内。窗户关闭后，我如何处理它

提前谢谢