从ParentViewModel到子用户控件的WPF绑定不工作

忽略了代码片段中不相关的内容(比如私有成员声明)

视图模型:

public class LinearGaugeViewModel<T> : INotifyPropertyChanged where T : GaugeElementViewModel
{
    public double Value
    {
        get => _value;
        set
        {
            _value = value;
            OnPropertyChanged();
        }
    }
}

“父”用户控件的XAML:

<ItemsControl ItemsSource="{Binding Elements}">
    <ItemsControl.Resources>
        <DataTemplate DataType="{x:Type local:HorizontalGaugeElementViewModel}">
            <local:HorizontalGaugeElement Value="{Binding RelativeSource={RelativeSource AncestorType=UserControl}, Path=DataContext.Value, Mode=OneWay}"/>
        </DataTemplate>
    </ItemsControl.Resources>
</ItemsControl>

public static DependencyProperty ValueProperty = DependencyProperty.Register(
    nameof(Value),
    typeof(double),
    typeof(HorizontalGaugeElement));

public double Value
{
    get => (double) GetValue(ValueProperty);
    set => SetValue(ValueProperty, value);
}

我想要 Value LinearGaugeViewModel HorizontalGaugeElement .

当我更改值时,我可以看到setter LinearGaugeViewModel.Value

public event PropertyChangedEventHandler PropertyChanged;

[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

仍然是的,dependency属性中的设置从未设置。

我做错什么了?