What is the event that is raised before the Docked child is closed in the DockingManager?

//Code shows how to use the windowclosing event in the DockingManager.
using Syncfusion.Windows.Tools.Controls;
namespace DockingManager
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
        DockingManager dockingmanager = new DockingManager();
        dockingmanager.WindowClosing += dockingmanager_WindowClosing;
        }
 //window closing event used to raise the event on closing dock and float child
        void dockingmanager_WindowClosing(object sender, WindowClosingEventArgs e)
        {
        }
    }
    }