ขอความช่วยเหลือ การทำ NavBarDragDrop (Devexpress) on C#

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        NavBarGroup _hittedGroup;

        public NavBarGroup HittedGroup
        {
            get { return _hittedGroup; }
            set { _hittedGroup = value; }
        }

        Point _hittedPoint;

        private void navBarControl1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left )
            {
                NavBarControl navBarControl = sender as NavBarControl;
                NavBarHitInfo info = navBarControl.CalcHitInfo(new Point(e.X, e.Y));
                if (info.HitTest == NavBarHitTest.GroupClient)
                    navBarControl.Cursor = Cursors.SizeNS;
                else
                    navBarControl.Cursor = Cursors.Default;

                if (HittedGroup != null)
                {
                    HittedGroup.GroupClientHeight += (e.Location.Y - _hittedPoint.Y);
                    _hittedPoint = e.Location;
                    ((NavBarControl)sender).DoDragDrop(navBarControl1.SelectedLink, DragDropEffects.Copy);
                }

            }
        }

        private void navBarControl1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && Control.ModifierKeys == Keys.None)
            {
                NavBarControl navBarControl = sender as NavBarControl;
                NavBarHitInfo info = navBarControl.CalcHitInfo(e.Location);
                if (info.HitTest == NavBarHitTest.GroupClient)
                {
                    HittedGroup = info.Group;
                    _hittedPoint = e.Location;
                }
            }
        }

        private void navBarControl2_DragOver(object sender, DragEventArgs e)
        {
            e.Effect = DragDropEffects.Copy;
        }
        private void navBarControl2_DragEnter(object sender, DragEventArgs e)
        {
            e.Effect = DragDropEffects.Copy;
        }

        private void navBarControl2_DragDrop(object sender, DragEventArgs e)
        {
            NavBarControl nb = sender as NavBarControl;
            NavBarItem nodes = (NavBarItem)e.Data.GetData(typeof(NavBarItem));
            if (nodes != null)
            {
                Point pt = nb.PointToClient(new Point(e.X, e.Y));
                NavBarHitInfo hi = nb.CalcHitInfo(pt);
                if (hi.InGroup)
                {
                    NavBarItemLink itemLink = hi.Group.AddItem();
                    itemLink.Item.Caption = "xx";
                    /*  for (int i = 0; i < nodes.LinkClicked; i++)
                      {
                          string dragString = GetStringByNode(nodes[i]);
                          NavBarItemLink itemLink = hi.Group.AddItem();
                          itemLink.Item.Caption = dragString;
                      }*/
                }
            }
        }


    }