How to restrict the dockability of child window to client area in WPF DockingManager?

<syncfusion:DockingManager x:Name="dockingmanager">
  <syncfusion:DockingManager.ClientControl>
    <ContentControl Name="ClientArea" syncfusion:DockingManager.DesiredWidthInDockedMode="700" syncfusion:DockingManager.SideInDockedMode="Left"/>
  </syncfusion:DockingManager.ClientControl>
  <ContentControl x:Name="Media" syncfusion:DockingManager.Header="Dock1" syncfusion:DockingManager.SideInDockedMode= "Bottom" />
  <ContentControl x:Name="Timeline" syncfusion:DockingManager.Header="Dock2"  syncfusion:DockingManager.SideInDockedMode="Bottom" />
  <ContentControl syncfusion:DockingManager.Header="Dock3" syncfusion:DockingManager.DesiredWidthInDockedMode="300" syncfusion:DockingManager.SideInDockedMode="Right" Name="Properties"/>
  <ContentControl x:Name="playlist" syncfusion:DockingManager.Header="Dock4" syncfusion:DockingManager.DesiredWidthInDockedMode="240"  syncfusion:DockingManager.SideInDockedMode= "Tabbed" syncfusion:DockingManager.TargetNameInDockedMode="Properties" />            
</syncfusion:DockingManager>

public partial class MainWindow : Window
{
  public MainWindow()
  {
    InitializeComponent();
    dockingmanager.PreviewMouseDown += Dockingmanager_PreviewMouseDown;
    dockingmanager.PreviewMouseUp += Dockingmanager_PreviewMouseUp;
    dockingmanager.PreviewMouseMove += Dockingmanager_PreviewMouseMove;            
  }       
       
  bool isMouseDown = false;
  bool isDragging = false;
  Point mouseDownPoint;
  Point mousePoint;
  DockedElementTabbedHost draggedelement = null;
  List<FrameworkElement> tabs = null;
  private void Dockingmanager_PreviewMouseUp(object sender, MouseButtonEventArgs e)
  {
    if (draggedelement != null && tabs != null)
    {
      foreach(var element in tabs)
      {
        if (DockingManager.GetDockAbility(element as FrameworkElement) == DockAbility.None)
          DockingManager.SetState(element as FrameworkElement, DockState.Dock);
          DockingManager.SetDockAbility(element as FrameworkElement, DockAbility.All);
      }                
    }
    isMouseDown = false;
    isDragging = false;                      
    tabs = null;
    draggedelement = null;
  }
 
  internal bool IsPointInsideElement(UIElement element)
  {
    Point pt = Mouse.GetPosition(element);
    Point point =  element.TranslatePoint(new Point(0, 0), this.dockingmanager);
    return pt.X > -5 && pt.Y > -5 && pt.X < point.X + element.RenderSize.Width && pt.Y < point.Y + element.RenderSize.Height;
  }
       
  private void Dockingmanager_PreviewMouseMove(object sender, MouseEventArgs e)
  {
    if (isMouseDown)
    {
      mousePoint = e.GetPosition(e.OriginalSource as IInputElement);
      draggedelement = VisualUtils.FindAncestor(dockingmanager.ActiveWindow, typeof(DockedElementTabbedHost)) as DockedElementTabbedHost;
 
      if (Math.Abs(mousePoint.X - mouseDownPoint.X) > 4 || Math.Abs(mousePoint.Y - mouseDownPoint.Y) > 4)
      {
        isDragging = true;
      }
      if (isDragging)
      {
        if (draggedelement != null && draggedelement.TabChildren != null && draggedelement.TabChildren.Count > 0)
        {
          tabs = new List<FrameworkElement>(draggedelement.TabChildren);
          if (tabs != null)
          {
            if (IsPointInsideElement(ClientArea))
            {                               
              foreach (var element in tabs)
              {
                DockingManager.SetDockAbility(element as FrameworkElement, DockAbility.None);
              }
            }
            else if (!IsPointInsideElement(ClientArea))
            {                                
              foreach (var element in tabs)
              {
                DockingManager.SetDockAbility(element as FrameworkElement, DockAbility.All);
              }
            }
          }
        }
      }
    }
  }
             
  private void Dockingmanager_PreviewMouseDown(object sender, MouseButtonEventArgs e)
  {
    isMouseDown = true;            
    mouseDownPoint = e.GetPosition(e.OriginalSource as IInputElement);
  }
}