c# – 解决方法以避免“无法创建默认转换器以在类型’Derived_N

public class Base {}
public class Derived_1 : Base {}
public class Derived_2 : Base {}
// more descendants...
public class Derived_N : Base {}

此层次结构中的类型用作视图模型中的查找列表：

public class SomeViewModel
{
    // available items
    public IEnumerable<Derived_N> SomeItems { get; }

    // currently selected item
    public Derived_N SelectedItem { get; set; }

    // there could be several property pairs as above
}

要从查找列表中选择值,我已经创建了用户控件(某种选择器).从选择过程开始,所有Base后代看起来都相似,用户控件操作Base类型属性：

public IEnumerable<Base> ItemsSource
    {
        get { return (IEnumerable<Base>)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty,value); }
    }

    public static readonly DependencyProperty ItemsSourceProperty =
        DependencyProperty.Register("ItemsSource",typeof(IEnumerable<Base>),typeof(BaseSelector),new PropertyMetadata(null));

    public Base SelectedItem
    {
        get { return (Base)GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty,value); }
    }

    public static readonly DependencyProperty SelectedItemProperty =
        DependencyProperty.Register("SelectedItem",typeof(Base),new FrameworkPropertyMetadata(null,FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));

XAML通常看起来像：

<myCtrls:BaseSelector ItemsSource="{Binding SomeItems}"
                      SelectedItem="{Binding SelectedItem}"/>

这按预期工作,但有这样的绑定错误：

Cannot create default converter to perform ‘two-way’ conversions
between types ‘Derived_N’ and ‘Base’

我知道,为什么它们在输出窗口中 – 理论上,SelectedItem可以是任何类型,派生自Base,但实际上这不是我的情况.
如果这个转换器错误消失：

public class DummyConverter : IValueConverter
{
    public object Convert(object value,Type targetType,object parameter,CultureInfo culture)
    {
        return value;
    }

    public object ConvertBack(object value,CultureInfo culture)
    {
        return value;
    }
}

用于绑定：

<myCtrls:BaseSelector ItemsSource="{Binding SomeItems}"
                      SelectedItem="{Binding SelectedItem,Converter={StaticResource DummyConverterKey}}"/>

但我根本不想使用它 – 正如你所看到的那样,转换器中没有任何有效载荷(虽然有很多这样的属性).

还有其他解决方法吗？