Grid: Change arrows for child records

        public RadForm1()
        {
            InitializeComponent();

            this.radGridView1.CellFormatting += radGridView1_CellFormatting;
            this.radGridView1.Relations.AddSelfReference(this.radGridView1.MasterTemplate, "id", "pid");
            this.radGridView1.DataSource = GetSampleData();
        }

        private void radGridView1_CellFormatting(object sender, CellFormattingEventArgs e)
        {
            GridDataCellElement dataCellElement = e.CellElement as GridDataCellElement;

            if (dataCellElement != null && dataCellElement.SelfReferenceLayout != null )
            {
                if (  dataCellElement.SelfReferenceLayout.ExpanderItem != null)
                {
                    dataCellElement.SelfReferenceLayout.ExpanderItem.SignImage = dataCellElement.SelfReferenceLayout.ExpanderItem.Expanded ? Properties.Resources.chevron_down : Properties.Resources.chevron_up;
                }
                else
                { 
                    dataCellElement.SelfReferenceLayout.ExpanderItem.ResetValue(ExpanderItem.SignImageProperty, ValueResetFlags.Local);
                }
            }
        }

        private DataTable GetSampleData()
        {
            DataTable dt = new DataTable();

            DataColumn dc = new DataColumn();
            dc.ColumnName = "id";
            dc.DataType = typeof(int);
            dt.Columns.Add(dc);

            DataColumn dc1 = new DataColumn();
            dc1.ColumnName = "name";
            dc1.DataType = typeof(string);
            dt.Columns.Add(dc1);

            DataColumn dc2 = new DataColumn();
            dc2.ColumnName = "pid";
            dc2.DataType = typeof(int);
            dt.Columns.Add(dc2);

            DataRow dr = dt.NewRow();
            dr[0] = 0;
            dr[1] = "My Computer";
            dr[2] = DBNull.Value;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 1;
            dr[1] = @"C:\";
            dr[2] = 0;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 2;
            dr[1] = @"D:\";
            dr[2] = 0;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 3;
            dr[1] = "Program Files";
            dr[2] = 1;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 4;
            dr[1] = "Microsoft";
            dr[2] = 3;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 5;
            dr[1] = "Telerik";
            dr[2] = 3;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = 6;
            dr[1] = "WINDOWS";
            dr[2] = 1;
            dt.Rows.Add(dr);

            return dt;
        }