尝试更新ViewModel中的Ui属性时DispatcherQueue为空

人气:149 发布:2023-01-03 标签: desktop c# xaml data-binding winui-3

问题描述

在桌面应用程序的WinUI 3中,我有一个要更新的属性,该属性通过x:Bind绑定到该UI。

我希望像在WPF中一样使用Dispatcher进入UI线程,并避免在更新道具时IM遇到的线程错误:

System.Runtime.InteropServices.COMException: 'The application called an interface that was marshalled for a different thread. (0x8001010E (RPC_E_WRONG_THREAD))'

我只是不确定在WinUI3中如何操作,当我尝试时

DispatcherQueue.GetForCurrentThread().TryEnqueue(() =>
{
    AeParty.OnSyncHub = false; // Prop bound in ui using x:Bind
});

我收到此错误

DispatcherQueue.GetForCurrentThread()为空

我也试过了:

this.DispatcherQueue.TryEnqueue(() =>
{
    AeParty.OnSyncHub = false;
});

但无法编译:

然后我发现thisGitHub问题,所以我尝试:

SynchronizationContext.Current.Post((o) =>
{
    AeParty.OnSyncHub = false;

}, null);

这是可行的,但为什么我无法在我的VM中使用调度程序进入UI线程?

推荐答案

DispatcherQueue.GetForCurrentThread()在实际具有DispatcherQueue的线程上调用时只返回DispatcherQueue。如果在后台线程上调用它,则确实没有要返回的DispatcherQueue

所以诀窍是调用UI线程上的方法,并将返回值存储在一个变量中,然后从后台线程使用该变量,例如:

public sealed partial class MainWindow : YourBaseClass
{
    public MainWindow()
    {
        this.InitializeComponent();
    }

    public ViewModel ViewModel { get; } = new ViewModel();
}

public class ViewModel : INotifyPropertyChanged
{
    private readonly DispatcherQueue _dispatcherQueue = DispatcherQueue.GetForCurrentThread();

    public ViewModel()
    {
        Task.Run(() => 
        {
            for (int i = 0; i < 10; i++)
            {
                string val = i.ToString();
                _dispatcherQueue.TryEnqueue(() =>
                {
                    Text = val;
                });
                Thread.Sleep(2000);
            }
        });

    }
    private string _text;
    public string Text
    {
        get { return _text; }
        set { _text = value; NotifyPropertyChanged(nameof(Text)); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

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