将视图模型绑定到ComboBox

Question

我正在制作一个UWP应用，我已将ObservableCollection<EduRole>绑定到ComboBox。我可以看到ComboBox中填充的项目。但是我还需要设置它SelectedItem属性，这是我无法工作的。

XAML：

<ComboBox Name="EducationalLevelComboBoxUpdate"
    ItemsSource="{x:Bind EduRoleList, Mode=OneWay}"

    <!--IS THIS OKAY?-->
    SelectedItem="{x:Bind Path=User.EduRole.Read, Mode=OneWay}"

    PlaceholderText="Select educational role">
    <ComboBox.ItemTemplate>
        <DataTemplate x:DataType="viewModels:EduRoleViewModel">
            <TextBlock Text="{x:Bind Read}"/>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

来源：

  private ObservableCollection<EduRoleViewModel> EduRoleList { get; set; } = new ObservableCollection<EduRoleViewModel>();

视图模型：

public class EduRoleViewModel
{
    public string Key { get; set; }
    public string Read { get; set; }
}

User是一个名为UserViewModel的类的对象，该类具有EduRoleViewModel类型属性，该类是：

class UserViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    private EduRoleViewModel _eduRole;
    public EduRoleViewModel EduRole
    {
        get { return _eduRole; }
        set
        {
            _eduRole = value;
            this.OnPropertyChanged();
        }
    }

    public void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {            
        this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

我希望Read EduRole属性的UserViewModel属性为SelectedItem

的ComboBox