How to add separator line in WinForms SfComboBox dropdown iems?

private void DropDownListView_DrawItem(object sender, Syncfusion.WinForms.ListView.Events.DrawItemEventArgs e)
{
    bool isEnableDraw = (this.sfComboBox1.ComboBoxMode == ComboBoxMode.MultiSelection && this.sfComboBox1.AllowSelectAll && this.sfComboBox1.DropDownListView.ShowCheckBoxes && e.ItemIndex == 0) ? false : (e.ItemData as Student).IsDraWSeparator;
    if (isEnableDraw)
    {
        e.Handled = true;
        var listView = sender as SfListView;
        var linearLayout = listView.GetType().GetProperty("LinearLayout", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).GetValue(listView);
        var items = linearLayout.GetType().GetProperty("Items").GetValue(linearLayout) as List<ListViewItemInfo>;
        var checkBoxStyle = items[e.ItemIndex].GetType().GetProperty("CheckBoxStyle", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
        checkBoxStyle.SetValue(items[e.ItemIndex], listView.Style.CheckBoxStyle);
        //Fill the background color of mouse hover item.
        if (e.ItemIndex == mouseHoverItemIndex)
            e.Graphics.FillRectangle(new SolidBrush(listView.Style.SelectionStyle.HoverBackColor), e.Bounds);
        //Fill the background color of Selecteditem.
        if (sfComboBox1.SelectedIndex == e.ItemIndex)
            e.Graphics.FillRectangle(new SolidBrush(listView.Style.SelectionStyle.SelectionBackColor), new RectangleF(e.Bounds.X, e.Bounds.Y, e.Bounds.Width, e.Bounds.Height - 2));
        RectangleF bounds = new RectangleF(e.Bounds.X + 2, e.Bounds.Y + 2, e.Bounds.Width, e.Bounds.Height);
        //Draw the checkbox if MultiSelction and showcheckboxes are enabled.
        if (sfComboBox1.ComboBoxMode == ComboBoxMode.MultiSelection && this.sfComboBox1.DropDownListView.ShowCheckBoxes)
        {
            CheckBoxPainter.DrawCheckBox(e.Graphics, new Rectangle(e.Bounds.X + 2, e.Bounds.Y + 2, e.Bounds.Width, e.Bounds.Height - 2), listView.CheckedItems.Contains(e.ItemData) ? CheckState.Checked : CheckState.Unchecked, listView.Style.CheckBoxStyle);
            bounds = new RectangleF(e.Bounds.X + 20, e.Bounds.Y + 2, e.Bounds.Width, e.Bounds.Height - 2);
        }
        //Draw the listview item text.
        e.Graphics.DrawString((e.ItemData as Student).StudentName, this.Font, new SolidBrush(Color.FromArgb(255, 51, 51, 51)), bounds);
        //Draw the separator line.
        e.Graphics.DrawLine(new Pen(Color.Gray, width: 1) { DashPattern = new[] { 2f, 2f } }, e.Bounds.Left, e.Bounds.Bottom - 1, e.Bounds.Right, e.Bounds.Bottom - 1);
    }
}
 
int mouseHoverItemIndex = -1;
 
private void SfComboBox1_MouseMove(object sender, MouseEventArgs e)
{
    var list = (sender as SfListView);
    //Get the mouse over item index using mouse location.
    mouseHoverItemIndex = (sender as SfListView).GetRowIndexAtPoint(e.Location);
    list.Invalidate();
}