Question

我发现了一些silimar问题，但这些并不是我所需要的。我想将stackpanel“IsEnabled”值绑定到我的项目的bool“！IsIterrupted”值。这是我的XAML文件：

<ListView ItemsSource="{Binding Path=Items}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel IsEnabled="{Binding !IsInterrupted, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}">
                    <Button Command="{Binding Path=StopThreadCommand, Source={StaticResource viewModel}}" CommandParameter="{Binding Id}"/>
                </StackPanel>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

这是项目的样子：

public class ThreadDecorator : BaseThread , INotifyPropertyChanged
{
    ...
    public event PropertyChangedEventHandler PropertyChanged;

    private bool _is_interrupted;
    public bool IsInterrupted
    {
        get { return _is_interrupted; }
        set
        {
            _is_interrupted = value;
            OnPropertyChanged("IsInterrupted");
        }
    }

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    ...
}

我的ViewModel：

public class ThreadsViewModel : DependencyObject
{

    private ThreadsModel _model;
    public ThreadsModel Model
    {
        get { return _model; }
        set
        {
            _model = value;
        }
    }

    public ICollectionView Items
    {
        get { return (ICollectionView)GetValue(ItemsProperty); }
        set { SetValue(ItemsProperty, value); }
    }

    public static readonly DependencyProperty ItemsProperty =
        DependencyProperty.Register("Items", typeof(ICollectionView), typeof(ThreadsViewModel), new PropertyMetadata(null));

    public StopThreadCommand StopThreadCommand { get; set; }

    public ThreadsViewModel()
    {
        this.Model = new ThreadsModel();
        Items = CollectionViewSource.GetDefaultView(Model.Threads);
        this.StopThreadCommand = new StopThreadCommand(this);
    }

    public void InterruptThread(int id)
    {
        _model.InterruptThread(id);
    }
}

StopThreadCommand：

public class StopThreadCommand : ICommand
{
    public ThreadsViewModel ViewModel {get; set;}
    public StopThreadCommand(ThreadsViewModel viewModel)
    {
        this.ViewModel = viewModel;
    }

    public bool CanExecute(object parameter)
    {
        return true;
    }

    public void Execute(object parameter)
    {
        this.ViewModel.InterruptThread((int)parameter);
    }
}

当我单击“停止”按钮时，IsInterrupted值将从false更改为true，并且必须禁用stackpanel，但UI不会更新。求救！

Answer 1

Binding is Path的默认属性，它是DataContext的属性/子属性的路径。它不是一个任意的C＃表达式。因此，您要将Binding.Path设置为"!IsInterrupted"。 !IsInterrupted不会评估IsInterrupted的布尔逆;它不会评估任何东西。它会在调试输出流中找到你：

System.Windows.Data错误：40：BindingExpression路径错误：＆＃39;！IsInterrupted＆＃39;在＆＃39; object＆＃39;上找不到的属性＆＃39; ThreadDecorator＆＃39; blah blah blah

<StackPanel 
    IsEnabled="{Binding !IsInterrupted, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}">

这样做的一种方法是write a boolean-inverse value converter（来自Chris Nicol的逐字逐句that link的另一端的答案）：

[ValueConversion(typeof(bool), typeof(bool))]
public class InverseBooleanConverter: IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        if (targetType != typeof(bool))
            throw new InvalidOperationException("The target must be a boolean");

        return !(bool)value;
    }

    public object ConvertBack(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException();
    }

    #endregion
}

用法：

<UserControl.Resources>
    <local:InverseBooleanConverter x:Key="InverseBooleanConverter" />
</UserControl.Resources>

<!-- stuff etc. -->

IsEnabled="{Binding Path=IsReadOnly, Converter={StaticResource InverseBooleanConverter}}"

如果DataTrigger为真，您还可以使用IsEnabled来编写样式，将False设置为IsInterrupted。

WPF：双向数据绑定不起作用

1 个答案: