无法使用Prism从回调方法内导航

Question

我有一个使用WPF和Prism的小应用程序.我有我的shell和两个模块.我可以在"正常时尚"(例如点击按钮)之间成功地在它们之间导航,因此我知道它们已正确连接导航.但是,如果我执行一些在完成时触发事件的异步操作,我无法从该事件处理程序内部导航.我尝试的最后一件事是使用Event Aggregation将事件发布回UI线程,但它仍然没有导航.事件的订阅者成功获取事件并触发RequestNavigate(...),但UI不会更新.

现在,一些代码:我的第一个模块的viewmodel LoginModule:

public class LoginViewModel : ViewModelBase, ILoginViewModel, INavigationAware
{
    ...

    [ImportingConstructor]
    public LoginViewModel(IRegionManager regionManager, IUnityContainer container, IEventAggregator eventAggregator)
    {
        _regionManager = regionManager;
        _container = container;
        _eventAggregator = eventAggregator;
    }

    private DelegateCommand _Login;
    public DelegateCommand Login
    {
        get
        {
            if (_Login == null)
                _Login = new DelegateCommand(() => LoginHandler());
            return _Login;
        }
    }
    private void LoginHandler()
    {
        _client = new JabberClient();
        _client.Server = "gmail.com";
        _client.User = Username;
        _client.Password = Password;

        ...

        _client.OnAuthenticate += client_OnAuthenticate;
        _client.Connect();
    }

    private void client_OnAuthenticate(object sender)
    {
        Console.WriteLine("Authenticated!");
        _eventAggregator.GetEvent<UserAuthenticatedEvent>().Publish("");
    }

    public bool IsNavigationTarget(NavigationContext navigationContext)
    {
        return true;
    }
    ...
}

我的第二个模块的ViewModel RosterModule:

public class RosterViewModel : IRosterViewModel, INavigationAware
{
    private readonly IEventAggregator _eventAggregator;
    private readonly IRegionManager _regionManager;

    [ImportingConstructor]
    public RosterViewModel(IRegionManager regionManager, IEventAggregator eventAggregator)
    {
        _regionManager = regionManager;
        _eventAggregator = eventAggregator;

        _eventAggregator.GetEvent<UserAuthenticatedEvent>().Subscribe(o =>
        {
            Console.WriteLine("Requesting navigation...");
            _regionManager.RequestNavigate(RegionNames.ContentRegion, new Uri(WellKnownViewNames.RosterView, UriKind.Relative));
        });
    }

    public bool IsNavigationTarget(NavigationContext navigationContext)
    {
        return true;
    }

    public void OnNavigatedFrom(NavigationContext navigationContext)
    {

    }

    public void OnNavigatedTo(NavigationContext navigationContext)
    {
        Console.WriteLine("I'm here at the RosterViewModel");
    }
}

关于我可能做错的任何提示？

Answer 1

从OP，

好吧，发布后几分钟，我重读了昨天遇到的一篇文章，发现了一些我错过的东西......

http://neverindoubtnet.blogspot.com/2009/05/event-aggregator-in-prism-explorer.html

他们解释说 Subscribe 方法的重载之一包括 ThreadOption。

所以：

_eventAggregator.GetEvent<UserAuthenticatedEvent>()
    .Subscribe(
    o =>
    {
        Console.WriteLine("Requesting navigation...");
        _regionManager.RequestNavigate(
            RegionNames.ContentRegion,
            new Uri(WellKnownViewNames.RosterView, UriKind.Relative));
    });

变成：

_eventAggregator.GetEvent<UserAuthenticatedEvent>()
    .Subscribe(
    o =>
    {
        Console.WriteLine("Requesting navigation...");
        _regionManager.RequestNavigate(
            RegionNames.ContentRegion,
            new Uri(WellKnownViewNames.RosterView, UriKind.Relative));
    }, 
    ThreadOption.UIThread);

现在可以了！

希望这能对其他人有所帮助。

享受！