Custom attached property

[limeniye]

I just wanna create attached property.

In the UWP I created attached property but this attached property does't work for NET6 pratfroms.
My xamlGenerator has issue for another platforms.

I readed Row attached property realization from Grid and also I Readed documentation. Its should be like next code:

[GeneratedDependencyProperty(DefaultValue = 0.0d, AttachedBackingFieldOwner = typeof(UIElement), Attached = true)]
public static readonly DependencyProperty LeftProperty = CreateLeftProperty();

public static double GetLeft(DependencyObject obj)
    => GetLeftValue(obj);

public static void SetLeft(DependencyObject obj, double value)
    => SetLeftValue(obj, value);

But GeneratedDependencyPropertyAttribute it is internal sealed class.

How can I create my custom attached property?

[limeniye]

The simple Example:

    public static class ExampleDataAp
    {
        public static readonly DependencyProperty DataProperty = 
            DependencyProperty.RegisterAttached("Data", typeof(FrameworkElement), typeof(ExampleDataAp),
                     new PropertyMetadata(false, OnDataChanged));

        private static void OnDataChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
        {
        }

        public static void SetData(UIElement element, FrameworkElement value)
        {
            element.SetValue(DataProperty, value);
        }
        public static FrameworkElement GetData(UIElement element)
        {
            return (FrameworkElement)element.GetValue(DataProperty);
        }
    }

            <ItemsControl.ItemContainerStyle>
                <Style TargetType="ContentPresenter">
                    <Setter Property="dragAPs:ExampleDataAp.Data" Value="{Binding ElementName=baseListView}"/>
                </Style>
            </ItemsControl.ItemContainerStyle>

Error

Severity	Code	Description	Project	File	Line	Suppression State
Error	CS1024	Preprocessor directive expected	DragPositionUnoProject.Skia.Wpf

[limeniye]

Sure.

[limeniye]

@jeromelaban, the repository and problems

[jeromelaban]

Thanks. This is a known issue #4826

[limeniye]

hm. If I understood correctly Uno doesn't support attached property?

[jeromelaban]

Uno does support attached properties properly, just not the setter syntax with a binding you're using in your sample.