How to restore the closed window in WPF DockingManager?

<Window x:Class="Application_New.MainWindow"
                 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                 xmlns:syncfusion="http://schemas.syncfusion.com/wpf"
                 Title="MainWindow" Height="350" Width="525">
 
      <Grid x:Name="Grid1">
           <Grid.RowDefinitions>
                <RowDefinition Height="40/>
                <RowDefinition Height="*”/>
           </Grid.RowDefinitions>
           <Button x:Name="Button1" Width="150" Height="23" Content="Restore the closed window" Click="Button1_Click" Grid.Row="0"/>
           <syncfusion:DockingManager x:Name="DockingManager" UseDocumentContainer="True" Grid.Row="1">
               <ContentControl syncfusion:DockingManager.Header="Child1"  x:Name="Content1"/>
               <ContentControl syncfusion:DockingManager.Header="Child2" x:Name="Content2"/>
               <ContentControl syncfusion:DockingManager.Header="Child3" x:Name="Content3"/>
           </syncfusion:DockingManager>
      </Grid>
</Window>

using Syncfusion.Windows.Tools.Controls;
namespace Application_New
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();  
        }
 
        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            DockingManager.ExecuteRestore(Content3, DockState.Dock);
        }
      
    }
}