C# 当ItemSource绑定到转换器时，SelectedValuePath在组合框中不起作用

我的课程如下：

public class VmUserNotification : BindableBaseThreadSafe
{
  private string _username;
        private EnumLocalizer<NotificationLevel> _notificationLevel;
        private List<EnumLocalizer<NotificationLevel>> _notificationOptions;

 public string Username
        {
            get => _username;
            set => Set(ref _username, value);
        }

        public EnumLocalizer<NotificationLevel> NotificationLevel
        {
            get => _notificationLevel;
            set => Set(ref _notificationLevel, value);
        }

        public List<EnumLocalizer<NotificationLevel>> NotificationOptions
        {
            get => _notificationOptions;
            set => Set(ref _notificationOptions, value);
        }
}

foreach (var user in usersWithNotificationLevelsOtherThanNone)
                {
                    var allOptions = new List<EnumLocalizer<NotificationLevel>>();
                    Enum.GetValues(typeof(NotificationLevel)).Cast<NotificationLevel>().ToList().ForEach(
                        logEventLevel => allOptions.Add(new EnumLocalizer<NotificationLevel>() { Value = logEventLevel }));

                    AlertSettings.UserNotificationListWithAllRoles.Add(new VmUserNotificationWithAllRoles()
                    {
                        Username = user.UserName,
                        NotificationOptions = allOptions,
                        NotificationLevel = allOptions.FirstOrDefault(x => x.Value == user.Notifications)
                    });

                }

在ViewModel中，我有一个VmUserNotificationWithAllRoles的ObservableCollection。我将其填充如下：

public class VmUserNotification : BindableBaseThreadSafe
{
  private string _username;
        private EnumLocalizer<NotificationLevel> _notificationLevel;
        private List<EnumLocalizer<NotificationLevel>> _notificationOptions;

 public string Username
        {
            get => _username;
            set => Set(ref _username, value);
        }

        public EnumLocalizer<NotificationLevel> NotificationLevel
        {
            get => _notificationLevel;
            set => Set(ref _notificationLevel, value);
        }

        public List<EnumLocalizer<NotificationLevel>> NotificationOptions
        {
            get => _notificationOptions;
            set => Set(ref _notificationOptions, value);
        }
}

foreach (var user in usersWithNotificationLevelsOtherThanNone)
                {
                    var allOptions = new List<EnumLocalizer<NotificationLevel>>();
                    Enum.GetValues(typeof(NotificationLevel)).Cast<NotificationLevel>().ToList().ForEach(
                        logEventLevel => allOptions.Add(new EnumLocalizer<NotificationLevel>() { Value = logEventLevel }));

                    AlertSettings.UserNotificationListWithAllRoles.Add(new VmUserNotificationWithAllRoles()
                    {
                        Username = user.UserName,
                        NotificationOptions = allOptions,
                        NotificationLevel = allOptions.FirstOrDefault(x => x.Value == user.Notifications)
                    });

                }

foreach（usersWithNotificationLevelsOtherThanNone中的var用户）
{
var allOptions=新列表（）；
Enum.GetValues（typeof（NotificationLevel））.Cast（）.ToList（）.ForEach(
logEventLevel=>allOptions.Add（新的EnumLocalizer（）{Value=logEventLevel}））；
AlertSettings.UserNotificationListWithAllRoles.Add（新建VmUserNotificationWithAllRoles（））
{
Username=user.Username，
NotificationOptions=allOptions，
NotificationLevel=allOptions.FirstOrDefault（x=>x.Value==user.Notifications）
});
}

在UI中，我使用转换器将组合框的itemsSource绑定到NotificationOptions。由于NotificationOptions将是一个可观察的列表集合，所以我有一个转换器。这是组合框

<ComboBox Margin="{StaticResource MarginAfterText}" 
                                              x:Name="NotificationsComboBox" 
                                              Grid.Column="2"
                                              ItemsSource="{Binding AlertSettings.UserNotificationListWithAllRoles,Converter={StaticResource TestConverter}}" 
                                              SelectedValuePath="NotificationLevel"
                                              Width="200">

这是我的转换器

public class TestConverter:IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, string language)
        {
            if(value is ObservableCollection<VmUserNotificationWithAllRoles> vmUserNotifications)
            {
                var item = vmUserNotifications.FirstOrDefault();
                if (item != null)
                {
                    return item.NotificationOptions;
                }
            }
            return null;
        }

        public object ConvertBack(object value, Type targetType, object parameter, string language)
        {
            throw new NotImplementedException();
        }
    }

公共类TestConverter:IValueConverter
{
公共对象转换（对象值、类型targetType、对象参数、字符串语言）
{
if（值为ObservableCollection vmUserNotifications）
{
var item=vmUserNotifications.FirstOrDefault（）；
如果（项！=null）
{
返回项。通知选项；
}
}
返回null；
}
公共对象转换回（对象值、类型targetType、对象参数、字符串语言）
{
抛出新的NotImplementedException（）；
}
}

---

问题是组合框没有选择值，它是空的。请帮忙。保留断点时，我可以看到NotificationLevel的值。

SelectedValuePath

仅与

SelectedValuePath

结合使用

例如，如果您有一个item类，如

public class Item
{
    string Value { get; set; }
}

具有如下视图模型

public class ViewModel : INotifyPropertyChanged
{
    public ObservableCollection<Item> Items { get; } = new ObservableCollection<Item>();

    public string SelectedItemValue { get; set; } // must fire PropertyChanged
}

公共类视图模型：INotifyPropertyChanged
{
公共ObservableCollection项{get；}=new ObservableCollection（）；
公共字符串SelectedItemValue{get；set；}//必须激发PropertyChanged
}

还有一个ItemsControl，如

<ItemsControl ItemsSource="{Binding Items}"
              SelectedValue="{Binding SelectedItemValue}"
              SelectedValuePath="Value">
    ...
</ItemsControl>

...

将

SelectedItemValue

属性设置为，例如

“Test”

将选择

值设置为
“Test”
的项目