How to add cascading menu items to the context menu in WinForms SyntaxEditor (EditControl)?

private void editControl1_MenuFill(object sender, System.EventArgs e)
{
    ContextMenuManager cmm = sender as ContextMenuManager;
    // Add a menu item to the context menu
    cmm.AddMenuItem("Bookmarks",new EventHandler(ToggleBookmark));
    // Add child menu items to the earlier menu item
    IContextMenuProvider contextMenuProvider =  this.editControl1.ContextMenuManager.ContextMenuProvider as IContextMenuProvider;
    contextMenuProvider.AddContextMenuItem("Bookmarks","Toggle Bookmarks",new EventHandler(ToggleBookmark));
    contextMenuProvider.AddContextMenuItem("Bookmarks","Clear Bookmarks",new EventHandler(ClearBookmarks));
    // Add a second level of child menu items to the earlier child menu item
    contextMenuProvider.AddContextMenuItem("Clear Bookmarks", "ClearAll", new EventHandler(ClearAllBookmarks));
    contextMenuProvider.AddContextMenuItem("Clear Bookmarks", "Clear", new EventHandler(ClearBookmark));
}

Private Sub editControl1_MenuFill(sender As Object, e As System.EventArgs) Handles editControl1.MenuFill
    Dim cmm As ContextMenuManager = sender
    ' Add a menu item to the context menu
    cmm.AddMenuItem("Bookmarks", New EventHandler(AddressOf ToggleBookmark))
    ' Add child menu items to the earlier menu item
    Dim contextMenuProvider As IContextMenuProvider =  Me.editControl1.ContextMenuManager.ContextMenuProvider
    contextMenuProvider.AddContextMenuItem("Bookmarks", "Toggle Bookmarks", New EventHandler(AddressOf ToggleBookmark))
    contextMenuProvider.AddContextMenuItem("Bookmarks", "Clear Bookmarks", New EventHandler(AddressOf ClearBookmarks))
    ' Add a second level of child menu items to the earlier child menu item
contextMenuProvider.AddContextMenuItem("Clear Bookmarks", "ClearAll", New  EventHandler(AddressOf ClearAllBookmarks))
    contextMenuProvider.AddContextMenuItem("Clear Bookmarks", "Clear", New EventHandler(AddressOf ClearBookmark))
End Sub 'editControl1_MenuFill