如何设置ComboBoxItem属性，实现ComboBox选中项隐藏并解决绑定问题

核心问题原因 #

• SortList 类未实现 INotifyPropertyChanged 接口，属性值变更后无法通知UI更新
• XAML 中 ComboBoxItem 的绑定路径错误，ComboBoxItem 的上下文本身就是单个 SortList 对象，无需加 Items. 前缀
• SortList 初始化时错误将所有项的 IsSelectable 设为 false，且选中新项时未重置旧选中项的状态
• XAML 中 Style 的 BasedOn 属性存在拼写错误，ComboBoxIem 应为 ComboBoxItem

代码修改 #

1. 修正 SortList 类，实现属性变更通知 #

using System.ComponentModel;
using System.Runtime.CompilerServices;

public class SortList : INotifyPropertyChanged
{
    private string _key;
    public string Key
    {
        get => _key;
        set
        {
            _key = value;
            OnPropertyChanged();
        }
    }

    private string _value;
    public string Value
    {
        get => _value;
        set
        {
            _value = value;
            OnPropertyChanged();
        }
    }

    private bool _isSelectable;
    public bool IsSelectable
    {
        get => _isSelectable;
        set
        {
            _isSelectable = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

2. 修正 ViewModel 逻辑 #

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();
        // 初始状态所有项都可选择
        s.IsSelectable = true;
        sl.Add(s);
    }
    _items = sl;
}

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

private SortList _selectedSort;
public SortList SelectedItem
{
    get => _selectedSort;
    set
    {
        if(_selectedSort != value)
        {
            // 重置之前选中项的可选状态
            if(_selectedSort != null)
            {
                _selectedSort.IsSelectable = true;
            }
            _selectedSort = value;
            // 新选中项设为不可选
            if(_selectedSort != null)
            {
                _selectedSort.IsSelectable = false;
            }
            PropertyChanged(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
        }
    }
}

3. 修正 XAML 代码 #

如果需要禁用已选中项，写法如下：

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

如果需要隐藏已选中项，修改Setter即可，WPF 原生支持 BooleanToVisibilityConverter 直接使用：

<!-- 先在页面/窗口资源中声明转换器 -->
<Window.Resources>
    <BooleanToVisibilityConverter x:Key="BoolToVisibilityConverter" />
</Window.Resources>

<!-- 然后修改Style中的Setter -->
<Setter Property="Visibility" Value="{Binding IsSelectable, Converter={StaticResource BoolToVisibilityConverter}}" />

额外说明 #

如果不需要后台的 comboSelectionChanged 事件逻辑可以直接删除，MVVM 模式下通过绑定即可完成所有逻辑，无需后台事件耦合。

内容的提问来源于stack exchange，提问作者gby