Attached property binding

MainWindow.xaml

<Window x:Class="WpfApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <StackPanel>
        <Label Content="{Binding Path=Content.(local:ViewProperty.Title), Mode=OneWay, Source={x:Reference Container}}"/>
        <Button Content="Button1" Click="Button1_Click"/>
        <Button Content="Button2" Click="Button2_Click"/>
        <ContentControl x:Name="Container" Height="100"/>
    </StackPanel>
</Window>

MainWindow.xaml.cs

namespace WpfApp
{
    using System.Windows;

    public partial class MainWindow
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            Container.Content = new UserControl1();
        }

        private void Button2_Click(object sender, RoutedEventArgs e)
        {
            Container.Content = new UserControl2();
        }
    }
}

UserControl1.xaml

<UserControl x:Class="WpfApp.UserControl1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:local="clr-namespace:WpfApp"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300"
             Background="Blue"
             local:ViewProperty.Title="Test1">
    <Grid>
    </Grid>
</UserControl>

UserControl2.xaml

<UserControl x:Class="WpfApp.UserControl2"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:local="clr-namespace:WpfApp"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300"
             Background="Red"
             local:ViewProperty.Title="Test2">
    <Grid>
    </Grid>
</UserControl>

ViewProperty.cs

namespace WpfApp
{
    using System.Windows;

    public static class ViewProperty
    {
        public static DependencyProperty TitleProperty = DependencyProperty.RegisterAttached(
            "Title",
            typeof(string),
            typeof(ViewProperty),
            new PropertyMetadata(string.Empty));

        public static string GetTitle(DependencyObject obj)
        {
            return (string)obj.GetValue(TitleProperty);
        }

        public static void SetTitle(DependencyObject obj, string value)
        {
            obj.SetValue(TitleProperty, value);
        }
    }
}