Question

I want to use a dependency property so that my label displays values selected in the Listbox. This is just to more clearly understand the working of a dependency property.

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:WPFToolkit="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit"
    xmlns:local="clr-namespace:WpfApplication1"
    x:Name="MyWindow"
    Height="200"
    Width="300">
       <StackPanel>
        <ListBox x:Name="lbColor"
                   Width="248"
                   Height="56"
                   ItemsSource="{Binding TestColor}"/>
       <StackPanel>
      <Label Content="{Binding Path=Test, ElementName=lbColor}" />
    </StackPanel>
  </StackPanel>
</Window>

Code Behind,

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {

        public ObservableCollection<string> TestColor { get; set; }

        public String Test
        {
            get { return (String)GetValue(TestProperty); }
            set { SetValue(TestProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Title.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty TestProperty =
            DependencyProperty.Register("Test", typeof(String), typeof(ListBox), new UIPropertyMetadata("Test1"));



        public Window1()
        {
            InitializeComponent();
            TestColor = new ObservableCollection<string>();
            DataContext = this;
            TestColor.Add("Red");
            TestColor.Add("Orange");
            TestColor.Add("Yellow");
            TestColor.Add("Green");
            TestColor.Add("Blue");
        }
    }
}

Can anyone explain to me how will I accomplish this using a dependency property? Somehow I am very confused with the Dependency Property concept, and I just wanted to see a working example for that.

Answer 1

You’ll need to have your ListBox “select” the current text:

<StackPanel>
    <!-- Add selected item binding -->
    <ListBox 
         x:Name="lbColor" Width="248" Height="56" 
         ItemsSource="{Binding TestColor}"
         SelectedItem="{Binding Test}"
    />

    <StackPanel>
        <!-- No need for elementname - just use Test on the DataContext -->
        <Label Content="{Binding Path=Test}" />
    </StackPanel>
</StackPanel>