How to roll up the float window to top in WPF DockingManager?

<Window x:Class="DockingManager_New1.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">
          <syncfusion:DockingManager x:Name="DockingManager1" UseDocumentContainer="True" IsRollupFloatWindow="True">
              <ContentControl syncfusion:DockingManager.Header="Child1" syncfusion:DockingManager.State="Dock"/>
              <ContentControl syncfusion:DockingManager.Header="Child2" syncfusion:DockingManager.State="Dock"/>
              <ContentControl syncfusion:DockingManager.Header="Child3" syncfusion:DockingManager.State="Dock"/>
           </syncfusion:DockingManager>
     </Grid>
</Window>

using Syncfusion.Windows.Tools.Controls;
namespace DockingManager_New1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DockingManager DockingManager1 = new DockingManager();
    // Setting IsRollUpFloatWindow property as True for the DockingManager
            DockingManager1.IsRollupFloatWindow = true;
            ContentControl content1 = new ContentControl();
            DockingManager.SetHeader(content1, "Child1");
            ContentControl content2 = new ContentControl();
            DockingManager.SetHeader(content2, "Child2");
            ContentControl content3 = new ContentControl();
            DockingManager.SetHeader(content3, "Child3");
            DockingManager1.Children.Add(content1);
            DockingManager1.Children.Add(content2);
            DockingManager1.Children.Add(content3);
            Grid1.Children.Add(DockingManager1);
        }
    }
}