WPF

<TextBox Text="{Binding ElementName=playlists, Path=SelectedItem.Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<ListBox Name="playlists" ItemsSource="{Binding Path=Files}" SelectionMode="Single">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Name}"/>
        </DataTemplate>          
    </ListBox.ItemTemplate>
</ListBox>

public class MyFile
{
    public string Name { get; set; }
}
   
public class Playist
{
    public ObservableCollection<myfile> Files { get; set; }

    public Playist()
    {
        Files = new ObservableCollection<myfile>();
        Files.Add(new MyFile { Name = "a" });
        Files.Add(new MyFile { Name = "b" });
        Files.Add(new MyFile { Name = "c" });
        Files.Add(new MyFile { Name = "d" });
    }
}

public partial class Window1 : Window
    {
        private PlayList _playlist = new PlayList();
        public Window1()
        {
            InitializeComponent();
            playlists.DataContext = _playlist;
        }
    }</myfile></myfile>

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel>
        <TextBox Text="{Binding ElementName=playlists, Path=SelectedItem.Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        <ListBox Name="playlists" ItemsSource="{Binding Path=Files}" SelectionMode="Single">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Name}"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
        <Button Content="Show file list from DC" Click="Button_Click" />
    </StackPanel>
</Window>

using System.Windows;
using System.Collections.ObjectModel;
using System.Text;

namespace WpfApplication1
{
    public partial class Window1 : Window
    {
        private PlayList _playlist = new PlayList();
        public Window1()
        {
            InitializeComponent();
            playlists.DataContext = _playlist;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            StringBuilder sb = new StringBuilder();
            foreach (MyFile file in _playlist.Files)
            {
                sb.Append(file.Name + " ");
            }
            MessageBox.Show(sb.ToString());
        }
    }

    public class MyFile 
    { 
        public string Name { get; set; } 
    }

    public class PlayList 
    {
        public ObservableCollection<MyFile> Files { get; set; }

        public PlayList() 
        {
            Files = new ObservableCollection<MyFile>();
            Files.Add(new MyFile { Name = "a" });
            Files.Add(new MyFile { Name = "b" });
            Files.Add(new MyFile { Name = "c" });
            Files.Add(new MyFile { Name = "d" }); 
        } 
    }
}

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:System="clr-namespace:System;assembly=mscorlib"
>
  <Page.Resources>
    <System:Double x:Key="myValue">10</System:Double>
  </Page.Resources>
  <Grid>  
    <TextBox Text="{Binding Source={StaticResource myValue}, Mode=OneWay}" />
  </Grid>
</Page>