C#•9mo ago

❔ User Control with custom dependency properties

I'm developing a user control that is supposed to have two properties bound by a parent control that will be using it. Initially, I developed the UC like I'm used to - View + ViewModel. However, I've quickly discovered that I need custom dependency properties that must be written into the View. So, in short, I need help to correctly propagate the bound values back to the ViewModel. In my Parent ViewModel, I have a

  public ObservableCollection<TemplateAttribute> Templates { get; } = new()
  {
    new TemplateAttribute("Height", AttributeType.Qualitative)
  };

  public ObservableCollection<TemplateAttribute> Templates { get; } = new()
  {
    new TemplateAttribute("Height", AttributeType.Qualitative)
  };

In my parent view, I'm using my custom user control:

<StackPanel Grid.Row="1">
  <Label Content="Attribute options" />
  <views:AttributeFilterBuilderControl TemplateAttributes="{Binding Templates}" />
</StackPanel>

<StackPanel Grid.Row="1">
  <Label Content="Attribute options" />
  <views:AttributeFilterBuilderControl TemplateAttributes="{Binding Templates}" />
</StackPanel>

UC View-behind:

public partial class AttributeFilterBuilderControl
{
  public static readonly DependencyProperty TemplateAttributesProperty =
    DependencyProperty.Register(nameof(TemplateAttributes),
      typeof(IEnumerable<TemplateAttribute>),
      typeof(AttributeFilterBuilderControl), new PropertyMetadata(Enumerable.Empty<TemplateAttribute>()));

  public IEnumerable<TemplateAttribute>? TemplateAttributes
  {
    get => (IEnumerable<TemplateAttribute>?)GetValue(TemplateAttributesProperty);
    set => SetValue(TemplateAttributesProperty, value);
  }

  public AttributeFilterBuilderControl() => InitializeComponent();
}

public partial class AttributeFilterBuilderControl
{
  public static readonly DependencyProperty TemplateAttributesProperty =
    DependencyProperty.Register(nameof(TemplateAttributes),
      typeof(IEnumerable<TemplateAttribute>),
      typeof(AttributeFilterBuilderControl), new PropertyMetadata(Enumerable.Empty<TemplateAttribute>()));

  public IEnumerable<TemplateAttribute>? TemplateAttributes
  {
    get => (IEnumerable<TemplateAttribute>?)GetValue(TemplateAttributesProperty);
    set => SetValue(TemplateAttributesProperty, value);
  }

  public AttributeFilterBuilderControl() => InitializeComponent();
}

UC VM property:

[ObservableProperty] private IEnumerable<TemplateAttribute>? m_templates;

[ObservableProperty] private IEnumerable<TemplateAttribute>? m_templates;

UC View:

  <UserControl.Style>
    <Style>
      <Setter Property="local:AttributeFilterBuilderControl.TemplateAttributes" Value="{Binding Templates, Mode=OneWayToSource}" />
    </Style>
  </UserControl.Style>

  <UserControl.Style>
    <Style>
      <Setter Property="local:AttributeFilterBuilderControl.TemplateAttributes" Value="{Binding Templates, Mode=OneWayToSource}" />
    </Style>
  </UserControl.Style>

From my debugging, it seems that the Parent Templates property getter is never called, and naturally, the setter of the dependency property is also never called. Any tips?

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