如何设置ComboBoxItem 属性？

Question

我试图在组合框中隐藏一个项目，当它被选中时，这就是我的代码现在的样子：

VeiwModel.cs

        public class SortList
        {
            public string Key { get; set; }
            public string Value { get; set; }
            public bool IsSelectable { get; set; }
        }
        private void InitSortList()
        {
            ObservableCollection<SortList> sl = new ObservableCollection<SortList>();

            foreach(var i in defaultSortList)
            {
                SortList s = new SortList();
                s.Key = i.Key.ToString();
                s.Value = i.Value.ToString();
                s.IsSelectable = false;
                sl.Add(s);
            }

            _items = sl;
        }

        private ObservableCollection<SortList> _items = new ObservableCollection<SortList>();
        public ObservableCollection<SortList> Items
        {
            get { 
                return _items; }
        }


        private SortList _selectedSort;
        public SortList SelectedItem
        {
            get { return _selectedSort; }
            set
            {
                if(_selectedSort != value)
                {
                    _selectedSort = value;
                    _selectedSort.IsSelectable = false;
                    PropertyChanged(this, new PropertyChangedEventArgs("SelectedItem"));
                }
            }
        }

MainPage.xaml

 <ComboBox Header="Sort 1" HorizontalAlignment="Stretch"
                                                  Name="Sort_1" SelectionChanged="comboSelectionChanged"
                                                  ItemsSource="{Binding Items, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                                                 SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
                                                  SelectedValuePath="Key"
                                            DisplayMemberPath="Value" 
                                                  >
                                            <ComboBox.ItemContainerStyle>
                                                <Style TargetType="ComboBoxItem" BasedOn="ComboBoxIem">
                                                    <Setter
                                                         Property="IsEnabled"
                                                         Value="{Binding Items.IsSelectable, Mode=TwoWay}" />

//Binding IsSelectable doesnt work either
                                                   
                                                </Style>
                                            </ComboBox.ItemContainerStyle>
                                        </ComboBox>

我不确定绑定部分如何在 Setter 属性上工作，因为我认为它没有从项目 class 中获取 IsSelectable 属性... .

Answer 1

请参考文档here，UWP 不支持样式设置器中的绑定。绑定ItemContainerStyle样式时不会生效。

Windows Presentation Foundation (WPF) and Microsoft Silverlight supported the ability to use a Binding expression to supply the Value for a Setter in a Style. The Windows Runtime doesn't support a Binding usage for Setter.Value (the Binding won't evaluate and the Setter has no effect, you won't get errors, but you won't get the desired result either). When you convert XAML styles from Windows Presentation Foundation (WPF) or Microsoft Silverlight XAML, replace any Binding expression usages with strings or objects that set values, or refactor the values as shared {StaticResource} markup extension values rather than Binding -obtained values.

对于这种情况，解决方法可以是一个助手 class，它具有绑定源路径的附加属性。它将在助手属性.

的 PropertyChangedCallback 代码中创建绑定表达式

我已经编辑了你的代码xaml，请参考下面的代码实现。

<Page.DataContext>
    <local:ViewModel />
</Page.DataContext>
<Grid>
    <ComboBox
        Name="Sort_1"
        HorizontalAlignment="Stretch"
        DisplayMemberPath="Value"
        Header="Sort 1"
        ItemsSource="{Binding Items, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
        SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
        SelectedValuePath="Key"
        SelectionChanged="comboSelectionChanged">
        <ComboBox.ItemContainerStyle>
            <Style TargetType="ComboBoxItem">
                <Setter Property="local:BindingHelper.IsEnable" Value="IsSelectable" />
            </Style>
        </ComboBox.ItemContainerStyle>
    </ComboBox>
</Grid>

C#代码

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();

    }

    private void comboSelectionChanged(object sender, SelectionChangedEventArgs e)
    {

    }
}

public class BindingHelper
{
    public static string GetIsEnable(DependencyObject obj)
    {
        return (string)obj.GetValue(IsEnableProperty);
    }
    public static void SetIsEnable(DependencyObject obj, string value)
    {
        obj.SetValue(IsEnableProperty, value);
    }
    // Using a DependencyProperty as the backing store for IsEnable.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty IsEnableProperty =
        DependencyProperty.RegisterAttached("IsEnable", typeof(string), typeof(BindingHelper), new PropertyMetadata(null, GridBindingPathPropertyChanged));

    private static void GridBindingPathPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        var propertyPath = e.NewValue as string;
        if (propertyPath != null)
        {
            var bindingProperty =
                e.Property == IsEnableProperty
                ? ComboBoxItem.IsEnabledProperty
                : null;
            BindingOperations.SetBinding(
                obj,
                bindingProperty,
                new Binding { Path = new PropertyPath(propertyPath) });
        }
    }
}

public class ViewModel : INotifyPropertyChanged
{
    public class SortList : INotifyPropertyChanged
    {
        public string Key { get; set; }
        public string Value { get; set; }
        private bool _isSelectable;
        public bool IsSelectable
        {
            get { return _isSelectable; }
            set
            {
                _isSelectable = value;
                OnPropertyChanged();
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged([CallerMemberName] string PropertyName = null)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(PropertyName));
            }
        }
    }
    public ViewModel()
    {
        defaultSortList = new Dictionary<string, string>();
        defaultSortList.Add("0", "item");
        defaultSortList.Add("1", "item1");
        defaultSortList.Add("2", "item2");
        defaultSortList.Add("3", "item3");

        InitSortList();
    }
    private Dictionary<string, string> defaultSortList;
    private void InitSortList()
    {
        ObservableCollection<SortList> sl = new ObservableCollection<SortList>();

        foreach (var i in defaultSortList)
        {
            SortList s = new SortList();
            s.Key = i.Key.ToString();
            s.Value = i.Value.ToString();
            s.IsSelectable = true;
            sl.Add(s);
        }

        _items = sl;
    }

    private ObservableCollection<SortList> _items = new ObservableCollection<SortList>();
    public ObservableCollection<SortList> Items
    {
        get
        {
            return _items;
        }
    }

    private SortList _selectedSort;
    public event PropertyChangedEventHandler PropertyChanged;
    public SortList SelectedItem
    {
        get { return _selectedSort; }
        set
        {
            if (_selectedSort != value)
            {
                _selectedSort = value;
                _selectedSort.IsSelectable = false;
                PropertyChanged(this, new PropertyChangedEventArgs("SelectedItem"));
            }
        }
    }
}

如何设置ComboBoxItem 属性？

How to set ComboBoxItem property?

c#

xaml

windows-runtime

winrt-xaml

winui-3