WPF登录加载窗口仅运行一次，线程跨访问异常求助

错误原因 #

首次运行后，proszeCzekaj对象已被关闭且关联的Dispatcher已调用InvokeShutdown，二次运行时仍尝试访问该已失效对象的Dispatcher，导致跨线程访问异常；同时线程资源未正确清理，残留的无效引用引发问题。

修复方案及代码修改 #

1. ViewModel.cs 修改（核心修复）

将全局的proszeCzekaj改为局部变量，确保每次登录都创建新的Loading窗口实例，同时优化线程和窗口关闭逻辑：

private async void ZalogujExecute(object obj)
{
    try
    {
        ProszeCzekaj proszeCzekaj = null;
        Thread loadingThread = new Thread(() =>
        {
            proszeCzekaj = new ProszeCzekaj();
            // 窗口关闭时终止Dispatcher循环，让线程自然退出
            proszeCzekaj.Closed += (sender2, e2) =>
            {
                if (proszeCzekaj.Dispatcher.Thread.IsAlive)
                {
                    proszeCzekaj.Dispatcher.BeginInvokeShutdown(DispatcherPriority.Normal);
                }
            };
            proszeCzekaj.Show();
            Dispatcher.Run(); // 启动Dispatcher循环，维持窗口线程
        });
        loadingThread.SetApartmentState(ApartmentState.STA);
        loadingThread.Start();

        // 等待登录验证完成
        var odp = await SprawdzLogowanie();
        if (odp == 1)
        {
            // 登录成功后的逻辑
        }

        // 安全关闭Loading窗口：检查窗口是否存在且Dispatcher未关闭
        if (proszeCzekaj != null && !proszeCzekaj.Dispatcher.HasShutdownStarted)
        {
            proszeCzekaj.Dispatcher.Invoke(() => proszeCzekaj.Close());
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

async Task<int> SprawdzLogowanie()
{
    await Task.Run(() =>
    {
        AplikacjaDbContext db = new AplikacjaDbContext();
        // 移除后台线程的MessageBox，避免UI阻塞和跨线程问题
        var users = db.UsersTable.ToList();
        // 测试可改为日志输出或其他非UI操作
    });
    return 1;
}

2. Loading.xaml.cs 优化（可选）

移除不必要的委托定义，直接调用窗口的Close方法，简化逻辑：

namespace PGSQL.View
{
    public partial class ProszeCzekaj : Window
    {
        public ProszeCzekaj()
        {
            InitializeComponent();
            IntPtr hWnd = new WindowInteropHelper(GetWindow(this)).EnsureHandle();
            var attribute = DWMWINDOWATTRIBUTE.DWMWA_WINDOW_CORNER_PREFERENCE;
            var preference = DWM_WINDOW_CORNER_PREFERENCE.DWMWCP_ROUND;
            DwmSetWindowAttribute(hWnd, attribute, ref preference, sizeof(uint));

            ProszeCzekajViewModel model = new ProszeCzekajViewModel();
            this.DataContext = model;
        }

        // 移除多余的委托，直接通过Close方法关闭窗口
        public enum DWMWINDOWATTRIBUTE
        {
            DWMWA_WINDOW_CORNER_PREFERENCE = 33
        }

        public enum DWM_WINDOW_CORNER_PREFERENCE
        {
            DWMWCP_DEFAULT = 0,
            DWMWCP_DONOTROUND = 1,
            DWMWCP_ROUND = 2,
            DWMWCP_ROUNDSMALL = 3
        }

        [DllImport("dwmapi.dll", CharSet = CharSet.Unicode, PreserveSig = false)]
        internal static extern void DwmSetWindowAttribute(IntPtr hwnd,
                                                         DWMWINDOWATTRIBUTE attribute,
                                                         ref DWM_WINDOW_CORNER_PREFERENCE pvAttribute,
                                                         uint cbAttribute);
    }
}

关键修复点说明 #

• 局部变量替代全局引用：每次登录创建新的Loading窗口，避免复用已释放的对象
• Dispatcher安全管理：窗口关闭时调用BeginInvokeShutdown让线程自然退出，而非强制终止
• 跨线程操作校验：关闭窗口前检查Dispatcher状态，确保操作在窗口所属线程执行
• 后台线程UI操作移除：移除SprawdzLogowanie中的MessageBox，后台线程禁止直接操作UI控件

内容的提问来源于stack exchange，提问作者McStar