How to get value of a property of the WPF ListBoxItem

Question

Hello I am trying to set the value of a property of my ListBoxItem, just not sure how to use Binding in this case if someone could help me, I appreciate it since!

Below XAML

<ControlTemplate TargetType="controls:ModernVerticalMenu">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="{TemplateBinding ListWidth}"/>
            <ColumnDefinition Width="{TemplateBinding ListWidth}"/>
            <ColumnDefinition Width="auto"/>
            <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <Border Background="{TemplateBinding BackColor}" Height="{TemplateBinding Height}" BorderThickness="1" BorderBrush="{DynamicResource bordaSuperior}">
            <!-- link list -->
            <ListBox x:Name="LinkList" ItemsSource="{Binding Links, RelativeSource={RelativeSource TemplatedParent}}"  
                                     ScrollViewer.HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}" >

                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <Grid Height="50" Background="Transparent" Width="500">
                            <Border Name="border" Padding="10">
                                <Path x:Name="icon" Data="{Binding IconData}" Stretch="Fill" Fill="{DynamicResource Accent}" Width="20" Height="20" HorizontalAlignment="Left" VerticalAlignment="Center" />
                            </Border>
                            <TextBlock x:Name="texto" ToolTip="{Binding Tooltip}"  Text="{Binding DisplayName}" Margin="45,2,2,2" FontSize="{DynamicResource MediumFontSize}" TextTrimming="CharacterEllipsis" VerticalAlignment="Center" HorizontalAlignment="Left" />
                        </Grid>
                        <DataTemplate.Triggers>
                            <DataTrigger Binding="{Binding IconData}" Value="{x:Null}">
                                <Setter Property="Margin" TargetName="texto">
                                    <Setter.Value>
                                        <Thickness Bottom="2" Top="2" Left="10" Right="2"/>
                                    </Setter.Value>
                                </Setter>
                            </DataTrigger>
                            <Trigger Property="IsMouseOver" Value="true">
                                <Trigger.Setters>
                                    <Setter Property="Fill" TargetName="icon">
                                        <Setter.Value>
                                            <SolidColorBrush Color="#f2f2f2" />
                                        </Setter.Value>
                                    </Setter>
                                </Trigger.Setters>
                            </Trigger>
                        </DataTemplate.Triggers>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </Border>
    </Grid>
    <ControlTemplate.Triggers>
        <Trigger Property="ListBoxItem.IsMouseOver" SourceName="LinkList" Value="true">
            <Trigger.Setters>

                <Setter Property="SelectedLinkGroup" Value="{Binding Source=LinkList,Path=Children}"/>
            </Trigger.Setters>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

In the code below I am trying to set the value SelectedLinkGroup From property to the value of Children referring to the ListBoxItem LinkList.

<Setter Property="SelectedLinkGroup" Value="{Binding Source=LinkList,Path=Children}"/>

using FirstFloor.ModernUI.Presentation;
using System;
using System.Data;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;

namespace FirstFloor.ModernUI.Windows.Controls
{
    /// <summary>
    /// Represents a control that contains multiple pages that share the same space on screen.
    /// </summary>
    public class ModernVerticalMenu
        : Control
    {
        /// <summary>
        /// Identifies the ContentLoader dependency property.
        /// </summary>
        public static readonly DependencyProperty ContentLoaderProperty = DependencyProperty.Register("ContentLoader", typeof(IContentLoader), typeof(ModernVerticalMenu), new PropertyMetadata(new DefaultContentLoader()));
        /// <summary>
        /// Identifies the ListWidth dependency property.
        /// </summary>
        public static readonly DependencyProperty ListWidthProperty = DependencyProperty.Register("ListWidth", typeof(GridLength), typeof(ModernVerticalMenu), new PropertyMetadata(new GridLength(170)));
        /// <summary>
        /// Identifies the Links dependency property.
        /// </summary>
        public static readonly DependencyProperty LinksProperty = DependencyProperty.Register("Links", typeof(LinkCollection), typeof(ModernVerticalMenu), new PropertyMetadata(OnLinksChanged));
        /// <summary>
        /// Identifies the SelectedSource dependency property.
        /// </summary>
        public static readonly DependencyProperty SelectedSourceProperty = DependencyProperty.Register("SelectedSource", typeof(Uri), typeof(ModernVerticalMenu), new PropertyMetadata(OnSelectedSourceChanged));
        /// <summary>
        /// Defines the SelectedLinkGroup dependency property.
        /// </summary>
        public static readonly DependencyProperty SelectedLinkGroupProperty = DependencyProperty.Register("SelectedLinkGroup", typeof(LinkCollection), typeof(ModernVerticalMenu), new PropertyMetadata(OnSelectedLinkGroupChanged));
        /// <summary>
        /// Defines the SelectedLink dependency property.
        /// </summary>
        public static readonly DependencyProperty SelectedLinkProperty = DependencyProperty.Register("SelectedLink", typeof(Link), typeof(ModernVerticalMenu), new PropertyMetadata(OnSelectedLinkChanged));
        /// <summary>
        /// Defines the SelectedLink dependency property.
        /// </summary>
        public static readonly DependencyProperty BackColorProperty = DependencyProperty.Register("BackColor", typeof(SolidColorBrush), typeof(ModernVerticalMenu), new PropertyMetadata(null));


        /// <summary>
        /// Occurs when the selected source has changed.
        /// </summary>
        public event EventHandler<SourceEventArgs> SelectedSourceChanged;

        private ListBox linkList;

        /// <summary>
        /// Initializes a new instance of the <see cref="ModernVerticalMenu"/> control.
        /// </summary>
        public ModernVerticalMenu()
        {
            this.DefaultStyleKey = typeof(ModernVerticalMenu);
            // this.BackColor = new SolidColorBrush(Color.FromRgb(0,0,255));

            // create a default links collection
            SetCurrentValue(LinksProperty, new LinkCollection());
        }

        private static void OnSelectedLinkGroupChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            // retrieve the selected link from the group
            var group = (LinkCollection)e.NewValue; // cria uma nova instancia do grupo
            Link selectedLink = null; //cria um link selecionado
              if (group != null)
              { //se o grupo copiado existe

                  selectedLink = group.FirstOrDefault();

              }

              // update the selected link
              ((ModernVerticalMenu)o).SetCurrentValue(SelectedLinkProperty, selectedLink);
        }

        private static void OnSelectedLinkChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            // update selected source
            var newValue = (Link)e.NewValue;
            Uri selectedSource = null;
            if (newValue != null)
            {
                selectedSource = newValue.Source;
            }
            ((ModernVerticalMenu)o).SetCurrentValue(SelectedSourceProperty, selectedSource);
        }


        private static void OnLinksChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            ((ModernVerticalMenu)o).UpdateSelection();
        }

        private static void OnSelectedSourceChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
        {
            ((ModernVerticalMenu)o).OnSelectedSourceChanged((Uri)e.OldValue, (Uri)e.NewValue);
        }

        private void OnSelectedSourceChanged(Uri oldValue, Uri newValue)
        {
            UpdateSelection();

            // raise SelectedSourceChanged event
            var handler = this.SelectedSourceChanged;
            if (handler != null) {
                handler(this, new SourceEventArgs(newValue));
            }
        }

        private void UpdateSelection()
        {
            if (this.linkList == null || this.Links == null) {
                return;
            }

            // sync list selection with current source
            this.linkList.SelectedItem = this.Links.FirstOrDefault(l => l.Source == this.SelectedSource);
           // SetValue(SelectedLinkGroupProperty, this.Links.FirstOrDefault(l => l.Children == this.SelectedLinkGroup));
            if (this.Links.FirstOrDefault(l => l.Children == this.SelectedLinkGroup) != null) { }

        }

        /// <summary>
        /// When overridden in a derived class, is invoked whenever application code or internal processes call System.Windows.FrameworkElement.ApplyTemplate().
        /// </summary>
        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();

            if (this.linkList != null) {
                this.linkList.SelectionChanged -= OnLinkListSelectionChanged;
            }

            this.linkList = GetTemplateChild("LinkList") as ListBox;
            if (this.linkList != null) {
                this.linkList.SelectionChanged += OnLinkListSelectionChanged;
            }

            UpdateSelection();
        }

        private void OnLinkListSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            //
            var link = this.linkList.SelectedItem as Link;
            if (link != null && link.Source != this.SelectedSource)
            {
                SetCurrentValue(SelectedSourceProperty, link.Source);

                SetCurrentValue(SelectedLinkGroupProperty, link.Children);
            }
        }

        /// <summary>
        /// Gets or sets the content loader.
        /// </summary>
        public IContentLoader ContentLoader
        {
            get { return (IContentLoader)GetValue(ContentLoaderProperty); }
            set { SetValue(ContentLoaderProperty, value); }
        }

        /// <summary>
        /// Gets or sets the collection of links that define the available content in this tab.
        /// </summary>
        public LinkCollection Links
        {
            get { return (LinkCollection)GetValue(LinksProperty); }
            set { SetValue(LinksProperty, value); }
        }

        /// <summary>
        /// Gets or sets the collection of links that define the available content in this tab.
        /// </summary>
        public LinkCollection SelectedLinkGroup
        {
            get { return (LinkCollection)GetValue(SelectedLinkGroupProperty); }
            set { SetValue(SelectedLinkGroupProperty, value); }
        }

        /// <summary>
        /// Gets or sets the collection of links that define the available content in this tab.
        /// </summary>
        public Link SelectedLink
        {
            get { return (Link)GetValue(SelectedLinkProperty); }
            set { SetValue(SelectedLinkProperty, value); }
        }

        /// <summary>
        /// Gets or sets the width of the list when Layout is set to List.
        /// </summary>
        /// <value>
        /// The width of the list.
        /// </value>
        public GridLength ListWidth
        {
            get { return (GridLength)GetValue(ListWidthProperty); }
            set { SetValue(ListWidthProperty, value); }
        }

        /// <summary>
        /// Gets or sets the source URI of the selected link.
        /// </summary>
        /// <value>The source URI of the selected link.</value>
        public Uri SelectedSource
        {
            get { return (Uri)GetValue(SelectedSourceProperty); }
            set { SetValue(SelectedSourceProperty, value); }
        }

        /// <summary>
        /// Gets or sets the source URI of the selected link.
        /// </summary>
        /// <value>The source URI of the selected link.</value>
        public SolidColorBrush BackColor
        {
            get { return (SolidColorBrush)GetValue(BackColorProperty); }
            set { SetValue(BackColorProperty, value); }
        }
    }
}

Answer 1

From my understanding of the code, you are trying to set the SelectedLinkGroup property to the items in your LinkList when your mouse is over a ListBoxItem.

As your LinkList's ItemsSource is bound to the Links property on your control you should be able to bind directly to this property to obtain the same result. The following code does just that.

Value="{Binding Links, RelativeSource={RelativeSource TemplatedParent}}"

Alternatively you could bind to the LinkList Items directly.

Value="{Binding ElementName=LinkList,  Path=ItemsSource}"

Here you specify the name of the element to bind to and the property on that element.