刷新 ComboBox with DropDown Opened 导致丢失选择

Question

我有一个包含活动网络接口条目的组合框。我喜欢在用户每次打开 DropDown 时刷新条目。

遗憾的是，如果 ComboBox 打开然后关闭（箭头在右侧），所选条目将不再显示。 ComboBox 显示为空。 My ComboBox before and after

如果我删除 DropDownOpened 事件，则在打开和关闭 DropDown 后，所选项目将显示在 ComboBox 中。

感谢您的帮助。

这是我的观点：

                    <ComboBox ItemsSource="{Binding HostInterfaces}"
                              SelectedItem="{Binding HostInterfaceSelected, Mode=TwoWay}"
                              DisplayMemberPath="Indicator">
                        <i:Interaction.Triggers>
                            <i:EventTrigger EventName="DropDownOpened">
                                <i:InvokeCommandAction Command="{Binding Path=DropDownOpenedCommand, Mode=OneWay}" />
                            </i:EventTrigger>
                        </i:Interaction.Triggers>
                    </ComboBox>

这是我的视图模型：

    private RelayCommand _dropDownOpenedCommand;
    public ICommand DropDownOpenedCommand => _dropDownOpenedCommand ??
                                             (_dropDownOpenedCommand =
                                                 new RelayCommand(ExecuteDropDownOpenedCommand));

    private void ExecuteDropDownOpenedCommand(object obj)
    {
        HostInterfaces.Clear();

        // add several entries
        _hostInterfaces.Add( ... );
    }

    private readonly ObservableCollection<HostNetworkInterfaceEntry> _hostInterfaces = new ObservableCollection<HostNetworkInterfaceEntry>();
    public ObservableCollection<HostNetworkInterfaceEntry> HostInterfaces => _hostInterfaces;
    private HostNetworkInterfaceEntry _hostInterfaceSelected;
    public HostNetworkInterfaceEntry HostInterfaceSelected
    {
        get => _hostInterfaceSelected;
        set
        {
            if (value == null) return;
            if (value == _hostInterfaceSelected) return;
            _hostInterfaceSelected = value;
            OnPropertyChanged(nameof(HostInterfaceSelected));
        }
    }

我的 HostNetWorkInterfaceEntry class:

public class HostNetworkInterfaceEntry
{
    public HostNetworkInterfaceEntry(string name, IPAddress address)
    {
        Name = name;
        Address = address;
    }

    public string Name { get; private set; }
    public IPAddress Address { get; private set; }
    public string Indicator => (Address != null ? $"{Address}   {Name}" : $"{Name}");
}

Answer 1

感谢@Senir 和@Jeroen van Langen。你的提示引导我找到解决方案。

我不得不修改属性 HostInterfaceSelected 和 ExecuteDropDownOpenedCommand 方法。

public HostNetworkInterfaceEntry HostInterfaceSelected
{
    get => _hostInterfaceSelected;
    set
    {
        // removed that -> if (value == null) return;
        if (value == _hostInterfaceSelected) return;
        _hostInterfaceSelected = value;
        OnPropertyChanged(nameof(HostInterfaceSelected));
    }
}

private void ExecuteDropDownOpenedCommand(object obj)
{
    var saveSelected = HostInterfaceSelected; // added this
    HostInterfaces.Clear();

    // add several entries
    _hostInterfaces.Add( ... );

    // restore saved to HostInterfaceSelected 
    if (saveSelected != null)
        HostInterfaceSelected = _hostInterfaces.FirstOrDefault(s => s.Name == saveSelected.Name && s.Address != null && s.Address.Equals(saveSelected.Address));
}

刷新 ComboBox with DropDown Opened 导致丢失选择

Refresh ComboBox with DropDownOpened result in loosing selected

c#

wpf

combobox