如何在后面的代碼中生成一個復選框并將其作為子項發送到MainWindow的邊框？

這張圖片是我關于 STA 執行緒的錯誤。

• 專案正在等待傳入資料。其實我不想只是等待申請。我正在嘗試使用調度程式或任務，但我遇到了這個錯誤。

  private async void Window_Loaded(object sender, RoutedEventArgs e)
        {
            ToggleStart();

            var stackPanel = await Task.Run(TaskCheckBoxZones).ConfigureAwait(false);
            ZonesBorder.Child = stackPanel;

        

         //await Dispatcher.BeginInvoke((Action)async delegate
         //{
           //  var findCheckBoxes = new FindCheckBoxes
            // {
               //  CheckBoxItemTab = CheckBoxPanel,
                // CheckBoxItemTab2 = CheckBoxPanel2,
                // Token = token,
            // };
            // await findCheckBoxes.LoadPaymentsMethods();
         //});



        }
        async Task<StackPanel> TaskCheckBoxZones()
        {
            var stackPanel = await new CreateCheckBoxZones()
            {
                Token = token
            }.LoadZonesData();

            return stackPanel;
        }

Settings.xaml.cs 中的上述代碼塊

public class CreateCheckBoxZones
    {
        private List<OrderZones> OrderZonesList;
        public string Token = "";
        public CreateCheckBoxZones()
        {
            OrderZonesList = new List<OrderZones>();
            _innerStack = new StackPanel();
        }

        //public Border Border;
        private StackPanel _innerStack;
        public StackPanel InnerStack
        {
            get { return _innerStack; }
            set { _innerStack = value; }
        }

        public async Task<StackPanel> LoadZonesData()
        {
            OrderZonesList = await MapOrderZones();

            foreach (var zone in OrderZonesList)
            {
                CheckBox cb = new CheckBox();
                cb.Tag = zone.Id;
                cb.Content = zone.Name;
                cb.IsChecked = zone.Status == 100;
                cb.Click  = ZonesCheckBox_Click;
                _innerStack.Children.Add(cb);
            }
            return _innerStack;
        }
        private async Task<List<OrderZones>> MapOrderZones()
        {
            var zoneModels = await TakeZones();

            if (zoneModels[0]._id == null)
                throw new Exception("Zones is can not null.");

            foreach (var zone in zoneModels)
            {
                OrderZonesList.Add(new OrderZones(
                    zone._id,
                    zone.placement,
                    zone.name.tr,
                    zone.minBasketSize,
                    zone.status,
                    zone.restaurant));
            }

            return OrderZonesList;
        }
        public async Task<List<ZoneModel>> TakeZones()
        {
            try
            {
                string url = Constants.GET_ZONES;

                var response = await new WebClient<List<ZoneModel>>()
                {
                    Endpoint = url,
                    Token = Token,
                    Method = Method.GET
                }.SendToAPIAsync();

                if (response.ErrorException != null)
                {
                    MessageBox.Show("B?lgeleri al?rken, bir hata ald?n.", "B?lgeler", MessageBoxButton.OK, MessageBoxImage.Error);
                }
                return response.Data;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            return null;
        }

上面的代碼塊是關于我的 LoadCheckbox 類，這個類使用我獲取資料的端點獲取一些 API 資訊，但是。在 UI 上選擇“定義”復選框時，我的應用程式凍結。我正在尋找一些解決方案。

uj5u.com熱心網友回復：

您應該使用 a ListBox（而不是 a StackPanel）和 aDataTemplate來生成專案（包括CheckBox）。

1. async永遠不要將方法包裝到Task.Run! 既然TaskCheckBoxZones是一種async方法，那Task.Run(TaskCheckBoxZones)就是禁忌。TaskCheckBoxZones或異步方法通常應以“異步”后綴命名，例如TaskCheckBoxZonesAsync. 這將幫助您識別異步方法以正確處理它們。
2. 你用ConfigureAwait(false)錯了。旨在通過允許繼續在執行緒池執行緒上執行ConfigureAwait(false)來避免背景關系切換回捕獲的內容。SynchronizationContext例如，當 aTask捕獲SynchronizationContext主執行緒的當前執行緒時，使用它配置它ConfigureAwait(false)可能會強制繼續，即 , 之后的代碼在await非 UI 執行緒上執行。
   在 UI 背景關系中使用ConfigureAwait(false)很可能會拋出InvalidOperationException指示非法的跨執行緒操作：

private void OnLoaded(object sender, EventArgs e)
{
  /** UI thread context **/

  // Task captures the current SynchronizationContext which is the UI thread.  
  var stackPanel = await Task.Run(TaskCheckBoxZones) // Never wrap an async method into a Task.Run
    .ConfigureAwait(false); // ConfigureAwait(false) will force continuation on a non UI thread.

  /** Worker thread context (non UI) **/

  ZonesBorder.Child = stackPanel; // Will throw InvalidOperationException (cross-thread)

要解決此問題，您通常不應ConfigureAwait(false)在 UI 背景關系中使用。它適用于非 UI 庫代碼。async在 UI 級別或應用程式級別背景關系中，您很可能希望在操作完成后回傳 UI 執行緒：

private void OnLoaded(object sender, EventArgs e)
{
  /** UI thread context **/

  // Task captures the current SynchronizationContext which is the UI thread.
  // Since ConfigureAwait(true) is the default behavior, the Task will return to the UI thread.  
  var stackPanel = await TaskCheckBoxZonesAsync(); 

  /** UI thread context **/

  ZonesBorder.Child = stackPanel; // Access allowed

3. 不要使用Dispatcher.BeginInvoke. 它是一種古老的方法，屬于 pre async/await API 時代的一部分。從 .NET Framework 4.5 開始，我們使用Dispatcher.InvokeAsync.
4. 不要將在 UI 執行緒上執行的代碼排入Dispatcher. 此外，在這種情況下等待Dispatcher絕對是多余的。規則 1) 也適用于：避免將方法Dispatcher包裝到呼叫中：asyncDispatcher

你的壞版本

await Dispatcher.BeginInvoke((Action)async delegate
{
  var findCheckBoxes = new FindCheckBoxes
  {
    CheckBoxItemTab = CheckBoxPanel,
    CheckBoxItemTab2 = CheckBoxPanel2,
    Token = token,
  };
  await findCheckBoxes.LoadPaymentsMethods();
});

正確的版本

var findCheckBoxes = new FindCheckBoxes
{
  CheckBoxItemTab = CheckBoxPanel,
  CheckBoxItemTab2 = CheckBoxPanel2,
  Token = token,
};
await findCheckBoxes.LoadPaymentsMethodsAsync();

5. Don't create a background thread only to create a control on the Dispatcher. This is absolutely pointless and expensive. If instantiation of your control is expensive consider to use an async initialization routine. Generally calling a constructor on a background thread is a serious code smell and an indicator of a poorly written class. A constructor must return immediately. A constructor should never be long-running:

Your bad version

private asnyc void OnButton_Click(object sender, EventArgs e)
{
  await Task.Run(() => Dispatcher.InvokeAsync(new MyDialogWindow().ShowDialog));
}

The correct version

private asnyc void OnButton_Click(object sender, EventArgs e)
{
  var dialog = new MyDialogWindow();
  await dialog.InitializeAsync(); // Perform longrunning and CPU intensive or IO initialization in a non blocking manner
  dialog.ShowDialog();
}

6. There is no reason to let a private method return a member (e.g., a property). Just make it return void.
7. Never catch the base class Exception and never show exception messages to the user. If you can recover from a particular exception, then only catch this one. Let the application crash on any other exception.

Solution

MainWindow.xaml.cs

partial class MainWIndow : Window
{
  // Use Clear, Add and Remove to modify this collection during runtime.
  // If you need to replace the complete collection (not recommended), then make this property into a dependency property.
  public ObservableCollection<OrderZone> OrderZones { get; }

  public MainWindow()
  {
    InitializeComponent();

    this.ZoneModels = new ObservableCollection<OrderZone>();
    this.Loaded  = onl oaded;
  }

  private async void OnLoaded(object sender, EventArgs e)
  {
    var zoneCreator = new OrderZoneCreator();
    IAsyncEnumerable<OrderZone> orderZones = zoneCreator.EnumerateOrderZonesAsync();
    await foreach (OrderZone orderZone in orderZones)
    {
      this.OrderZones.Add(orderZone);
    }
  }
}

ZoneModelCreator.cs

public class OrderZoneCreator
{
  public async IAsyncEnumerable<OrderZone> EnumerateOrderZonesAsync()
  {
    List<ZoneModel> zoneModels = await GetZonesAsync();
    foreach (var zone in zoneModels)
    {
      var newOrderZone = new OrderZone(
        zone._id,
        zone.placement,
        zone.name.tr,
        zone.minBasketSize,
        zone.status,
        zone.restaurant);

      yield return newOrderZone;
    }
  }

  private async Task<List<ZoneModel>> GetZonesAsync()
  {
    string url = Constants.GET_ZONES;
    var webClient = new WebClient<List<ZoneModel>>()
    {
      Endpoint = url,
      Token = Token,
      Method = Method.GET
    };
    var response = await webClient.SendToAPIAsync();
    if (response.ErrorException != null)
    {
      // This is an internal operation and shouldn't generate user messages 
      // as the user can't do anything to make this operation succeed.
      // Throw an exception if this error is not acceptable
      // or do nothing and return an empty collection.
      return new List<ZoneModel>();
    }

    return response.Data;
  }
}

StatusToBooleanConverter.cs

class StatusToBooleanConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    => value is OrderZone orderZone
      ? orderZone.Status == 100
      : Binding.DoNothing;
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
    => throw new NotSupportedException();
}

MainWindow.xaml

<Window>
  <Window.Resources>
    <local:StatusToBooleanConverter x:Key="StatusToBooleanConverter" />
  </Window.Resources>

  <ListBox ItemsSource="{Binding RelativeSource={RelativeSource AncestorType=Window}, Path=OrderZones}"
           BorderBrush="Black"
           BorderThickness=2>
    <ListBox.ItemTemplate>
      <DataTemplate DataType="{x:Type local:OrderZone}">
        <CheckBox Content="{Binding Name, Mode OneTime}"
                  Tag="{Binding Id, Mode OneTime}"
                  Click="ZonesCheckBox_Click"
                  IsChecked="{Binding Status, Converter={StaticResource StatusToBooleanConverter}, Mode OneTime}" />
      </DataTemplate>
    </ListBox.ItemTemplate>
  </ListBox>
</Window>

標籤：C＃ wpf 多线程 线程安全

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