wpfdatacontextadorneradornerlayer

No, an Adorner DOES NOT automagically take the DataContext of its AdornedElement in WPF


Original question: Does an Adorner automagically inherit the "DataContext" of its "AdornedElement" in WPF?


Solution

  • This proves (or can prove) that it doesn't:

    public class SomeObject
    { }
    
    public class SomeAdorner : Adorner
    {
        public SomeAdorner(UIElement adornedElement) : base(adornedElement)
        {
            // comment out the following statement to see that, by default, an adorner does not
            // take on the data context of its adorned ui element
            SetBinding(
                DataContextProperty,
                new Binding(DataContextProperty.Name)
                {
                    Mode = BindingMode.OneWay,
                    Source = adornedElement
                }
            );
        }
    
        protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
        {
            base.OnPropertyChanged(e);
    
            if ((e.Property.Name.Equals(DataContextProperty.Name)) && (e.NewValue is SomeObject))
            { MessageBox.Show("DataContext changed!"); }
        }
    }
    
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            Loaded += new RoutedEventHandler(Window1_Loaded);
        }
    
        void Window1_Loaded(object sender, RoutedEventArgs e)
        {
            AdornerLayer.GetAdornerLayer(WindowContentWithElementName)
                .Add(new SomeAdorner(WindowContentWithElementName));
    
            WindowContentWithElementName.DataContext = new SomeObject();
        }
    }