Silverlight XAML Binding ElementName

Question

I have the following XAML:

The height of the ItemsOfInterest is dynamic pending on how many elements are in it.

Anyone see what I am doing wrong with the height binding? It isn't even close to the same size as the ItemsOfInterst.

CodeNaked · Accepted Answer

You should bind to ActualHeight, which specifies the height it was arranged at. The Height property allows you to set a fixed height, but doesn't tell you exactly how tall it is when arranged.

EDIT:

Actually, this is a known bug with Silverlight.

You would have to use the SizeChanged event like so:

With a code-behind of:

using System.Windows;
using System.Windows.Controls;

namespace SilverlightApplication3 {
    public partial class MainPage : UserControl {
        public MainPage() {
            InitializeComponent();
        }

        private int counter;

        private void Button_Click(object sender, RoutedEventArgs e) {
            this.counter++;
            this.listBox1.Items.Add(counter.ToString());
        }

        private void listBox1_SizeChanged(object sender, SizeChangedEventArgs e) {
            this.listBox2.Height = this.listBox1.ActualHeight;
        }
    }
}

You could probably wrap this up into a nice attached behavior also.

EDIT: Here is such a behavior:

With a code-behind of:

using System;
using System.Windows;
using System.Windows.Controls;

namespace SilverlightApplication3 {
    public partial class MainPage : UserControl {
        public MainPage() {
            InitializeComponent();
        }

        private int counter;

        private void Button_Click(object sender, RoutedEventArgs e) {
            this.counter++;
            this.listBox1.Items.Add(counter.ToString());
        }
    }

    public static class SizeSynchronizationBehavior {

        #region Dependency Properties

        ///////////////////////////////////////////////////////////////////////////////////
        // HeightElement
        ///////////////////////////////////////////////////////////////////////////////////

        /// 
        /// Identifies the HeightElement attached dependency property.  This field is read-only.
        /// 
        /// The identifier for the HeightElement attached dependency property.
        public static readonly DependencyProperty HeightElementProperty = DependencyProperty.RegisterAttached("HeightElement",
            typeof(FrameworkElement), typeof(SizeSynchronizationBehavior), new PropertyMetadata(null, OnHeightElementPropertyValueChanged));

        /// 
        /// Gets the value of the  attached property for the specified .
        /// 
        /// The object to which the attached property is retrieved.
        /// 
        /// The value of the  attached property for the the specified .
        /// 
        public static FrameworkElement GetHeightElement(FrameworkElement obj) {
            if (obj == null) throw new ArgumentNullException("obj");
            return (FrameworkElement)obj.GetValue(HeightElementProperty);
        }

        /// 
        /// Sets the value of the  attached property to the specified .
        /// 
        /// The object to which the attached property is written.
        /// 
        /// The new value of the  attached property to the specified .
        /// 
        public static void SetHeightElement(FrameworkElement obj, FrameworkElement value) {
            if (obj == null) throw new ArgumentNullException("obj");
            obj.SetValue(HeightElementProperty, value);
        }

        /// 
        /// Called when  is changed.
        /// 
        /// The dependency object that was changed.
        /// The  instance containing the event data.
        private static void OnHeightElementPropertyValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
            FrameworkElement element = d as FrameworkElement;
            if (element == null)
                return;

            SizeChangedEventHandler heightSizeChangedEventHandler = GetSizeChangedEventHandler(element);
            if (heightSizeChangedEventHandler == null) {
                heightSizeChangedEventHandler = (sender, eventArgs) => {
                    FrameworkElement he = GetHeightElement(element);
                    if (he != null)
                        element.Height = he.ActualHeight;
                };
                SetSizeChangedEventHandler(element, heightSizeChangedEventHandler);
            }

            FrameworkElement heightElement = e.OldValue as FrameworkElement;
            if (heightElement != null)
                heightElement.SizeChanged += heightSizeChangedEventHandler;

            heightElement = e.NewValue as FrameworkElement;
            if (heightElement != null)
                heightElement.SizeChanged += heightSizeChangedEventHandler;

        }

        ///////////////////////////////////////////////////////////////////////////////////
        // SizeChangedEventHandler
        ///////////////////////////////////////////////////////////////////////////////////

        /// 
        /// Identifies the SizeChangedEventHandler attached dependency property.  This field is read-only.
        /// 
        /// The identifier for the SizeChangedEventHandler attached dependency property.
        private static readonly DependencyProperty SizeChangedEventHandlerProperty = DependencyProperty.RegisterAttached("SizeChangedEventHandler",
            typeof(SizeChangedEventHandler), typeof(SizeSynchronizationBehavior), new PropertyMetadata(null));

        /// 
        /// Gets the value of the  attached property for the specified .
        /// 
        /// The object to which the attached property is retrieved.
        /// 
        /// The value of the  attached property for the the specified .
        /// 
        private static SizeChangedEventHandler GetSizeChangedEventHandler(FrameworkElement obj) {
            if (obj == null) throw new ArgumentNullException("obj");
            return (SizeChangedEventHandler)obj.GetValue(SizeChangedEventHandlerProperty);
        }

        /// 
        /// Sets the value of the  attached property to the specified .
        /// 
        /// The object to which the attached property is written.
        /// 
        /// The new value of the  attached property to the specified .
        /// 
        private static void SetSizeChangedEventHandler(FrameworkElement obj, SizeChangedEventHandler value) {
            if (obj == null) throw new ArgumentNullException("obj");
            obj.SetValue(SizeChangedEventHandlerProperty, value);
        }

        #endregion // Dependency Properties
    }

}

Silverlight XAML Binding ElementName

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