使用调度程序通过 wpf 中的异步方法从 class 更新 UI

Question

我有一个带有管理数据的 class，这个 class 有一个绑定在 UI 菜单中的 ObservableCollection。问题是可观察集合加载数据，但我的 UI 没有显示它。

我的class是这样的

public class DAL : INotifyPropertyChanged
{
    public DAL()
    {
        this.unity = new UnitOfWork(@"http://192.168.0.173/vocalcontactapi");
    }

    private UnitOfWork unity;

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    private ObservableCollection<EstadosAgente> estadosPausa = new ObservableCollection<EstadosAgente>();
    public ObservableCollection<EstadosAgente> EstadosPausa
    {
        get { return this.estadosPausa; }
    }

    public async Task<bool> GetAgentStatesAsync()
    {
        await awaitGetAgentStatesTask();
        OnPropertyChanged("EstadosPausa");
        return true;
    }

    private Task awaitGetAgentStatesTask()
    {
        //UnitOfWork unity = new UnitOfWork(Properties.Settings.Default.restServer);
        NameValueCollection parms = new NameValueCollection();
        parms.Add("servicioId", "1");
        return Task.Run(() =>
        {
            try
            {
                var estados = unity.EstadosAgente.GetAll(parms).Where(q => q.habilitado == true).Select(p => p).ToList();
                if (estados == null)
                    return;

                estados.ForEach(x =>
                {
                    Application.Current.Dispatcher.Invoke(new Action(() =>
                    {
                        this.EstadosPausa.Add(x); //*** I think here is the problem***
                    }));
                });

            }
            catch (Exception ex)
            {
                string err = ex.Message;
            }
        });
    }

}

而 mainWindow 我有一个属性的 class DAL:

private DAL data = new DAL();
public DAL Data { get{ return this.data}}

在我的菜单中有下一个：

  <Menu Grid.Row="1">
            <MenuItem Header="uno" ItemsSource="{Binding DAL.EstadosPausa}" Click="DataBoundMenuItem_Click">
                <MenuItem.ItemContainerStyle>
                    <Style TargetType="MenuItem">
                        <Setter Property="Header" Value="{Binding estado}"/>
                        <Setter Property="Tag" Value="{Binding}" />
                    </Style>
                </MenuItem.ItemContainerStyle>
            </MenuItem>
        </Menu>

显然，加载数据的所有属性都是正确的。有什么帮助吗？

Answer 1

这段代码中有一些东西让我 "itchy" 但无论如何......

您有 public DAL Data 属性但您绑定到 DAL.EstadosPausa。您需要绑定到 Data.EstadosPausa 才能解决问题。您将在调试器中看到所有绑定错误 Output window.

在这里，考虑一下您的代码库的这个简化但 100% 工作的版本。现在你在玩 async/awaits，无缘无故地返回 Task<bool> 和 Dispatching 工作到 UI 线程（从你的例子中很明显）。

XAML

<Menu Grid.Row="1">
    <MenuItem Header="Uno" ItemsSource="{Binding Data.EstadosPausa}">
        <MenuItem.ItemContainerStyle>
            <Style TargetType="MenuItem">
                <Setter Property="Header" Value="{Binding Estado}"/>
                <Setter Property="Tag" Value="{Binding}" />
            </Style>
        </MenuItem.ItemContainerStyle>
    </MenuItem>
</Menu>

代码隐藏

public partial class MainWindow : Window
{
    private readonly Dal _data = new Dal();

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;

        _data.GetAgentStatesAsync(); // Fire Task away, no time to wait!!1
    }

    public Dal Data { get { return _data; } }  
}

public class EstadosAgente
{
    public string Estado { get; set; }
}

public class Dal : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public Task GetAgentStatesAsync()
    {
        return Task.Run(() =>
            {
                Thread.Sleep(1000); // I'm a long running operation...
                var estados = new List<EstadosAgente>
                    {
                        new EstadosAgente { Estado = "Estado 1" },
                        new EstadosAgente { Estado = "Estado 2" }
                    };
                EstadosPausa = new ObservableCollection<EstadosAgente>(estados);
                OnPropertyChanged("EstadosPausa");
            });
    }

    public ObservableCollection<EstadosAgente> EstadosPausa { get; private set; }

    private void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged; // <- always assign to local variable!
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

使用调度程序通过 wpf 中的异步方法从 class 更新 UI

using dispatcher to update UI from class with async methods in wpf

c#

asynchronous

class