wpf - 无法设置 CheckComboBox 中所选项目的初始状态

Question

我正在尝试使用Xceed CheckComboBox，它运行良好，除了一个小问题。最初加载 CheckComboBox 时，所选项目列表会正确显示在 CheckComboBox 的 ToggleButton 部分中，但不会选中代表这些项目的复选框。这是我正在使用的代码

XAML

<xctk:CheckComboBox x:Name="_combo"  Grid.Row="2" Grid.Column="1" 
                 ItemsSource="{Binding RoomFacilities}" 
                 HorizontalAlignment="Center" 
                 VerticalAlignment="Center"
                 DisplayMemberPath="FacilityName" 
                 SelectedItemsOverride="{Binding SelectedFaclities}" 
                    />

查看模型

public class RoomBandUpdateViewModel : Screen, IHandle<RecordChanged<RoomFacility>>,
                                               IHandle<RecordDeleted<RoomFacility>> {
    private ObservableCollection<RoomFacility> _roomFacilities;
    public ObservableCollection<RoomFacility> RoomFacilities {
        get { return _roomFacilities; }
        set { _roomFacilities = value; NotifyOfPropertyChange(() => RoomFacilities); }
    }

    private ObservableCollection<RoomFacility> _selectedFacilities;
    public ObservableCollection<RoomFacility> SelectedFaclities {
        get { return _selectedFacilities; }
        set { _selectedFacilities = value; NotifyOfPropertyChange(() => SelectedFaclities); }
    }

    protected override void OnActivate() {
        SelectedFaclities = new ObservableCollection<RoomFacility>(RoomBand.Facilities);
        RoomFacilities = new ObservableCollection<RoomFacility>(facilityService.GetAll());
    }
}

我想知道为什么当在 View 模型中正确设置 SelectedFacilities 时，CheckComboBox 的复选框不会根据 SelectedFacilities 中的项目进行选中。有趣的是，CheckComboBox 的切换按钮部分正确地以逗号分隔列表显示 SelectedFacilities。

Answer 1

不清楚你怎么填写SelectedFacilities和RoomFacilities 。确保您已处理 RoomFacility 的引用相等性正确。换句话说，我只能重现问题的唯一方法是当我填写ObservableCollection时采用以下模式:

RoomFacilities m1 = new RoomFacilities() { FacilityName = "F1" };
RoomFacilities m2 = new RoomFacilities() { FacilityName = "F2" };
RoomFacilities m3 = new RoomFacilities() { FacilityName = "F3" };
RoomFacilities m4 = new RoomFacilities() { FacilityName = "F1"};
RoomFacilities m5 = new RoomFacilities() { FacilityName = "F2"};
RoomFacilities = new ObservableCollection<RoomFacilities>(new Collection<RoomFacilities>() { m1, m2, m3 });
        SelectedFacilities = new ObservableCollection<RoomFacilities>(new Collection<RoomFacilities>() { m4, m5 });

请注意，虽然 m4和m5有类似的FacilityName (显示在 ToggleButton 的 CheckComboBox 中，它们不会在下拉面板中被选中，除非您重写 Equals 方法:

public override bool Equals(object obj)
{
    if (obj is RoomFacilities)
    {
        RoomFacilities mod = (RoomFacilities)obj;
        if (mod.FacilityName == this.FacilityName)
            return true;
        else
            return false;
    }
    return base.Equals(obj);
}
public override int GetHashCode()
{
    return FacilityName.GetHashCode();
}

换句话说，CheckComboBox如果 SelectedItemsOverride 则不会引发异常不是 ItemsSource 的子集